Complimentary polymer electrochromic device

ABSTRACT

A complimentary polymer or “dual-polymer” electrochromic device and methods of preparing the same are provided.

REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 13/677,197, filed Nov. 14, 2012, which claims the benefit ofU.S. Provisional Application No. 61/560,243, filed Nov. 15, 2011, theentirety of which are incorporated by reference herein.

FIELD OF THE INVENTION

Provided are conducting polymer (CP) compositions and electrochromicdevices containing the same. More particularly, this invention relatesto CP compositions and electrochromic devices responsive in thevisible-to-near-IR spectral region.

BACKGROUND OF THE INVENTION

Electrochromic Materials and Devices and Electrochromic ConductingPolymers

Electrochromic materials change color upon application of a voltage,generally a small (<5 V) DC voltage. The “color” change may be in thevisible spectral region, but it may also be in the near infrared (NIR),infrared and microwave spectral region. Electrochromic devices may betransmissive-mode, in which light passes through the device and ismodulated by the device, and reflective-mode, in which light isreflected off the device and also modulated by the device.Electrochromic devices may be used in windows, rear view automobilemirrors, flat panel displays, variable emittance materials forspacecraft application, and infrared camouflage.

The change in color of an electrochromic material is usually due to areduction/oxidation (“redox”) process within the electrochromicmaterial. Electrochromic materials active in the visible spectral regioninclude metal oxides, such as tungsten, molybdenum, nickel and tantalumoxides, showing a transition from highly colored to near transparentdepending on the potential (voltage) applied to them.

Another class of electrochromic materials are conducting polymers. Redoxof a conducting polymer, which changes its color as well asconductivity, is usually accompanied by an inflow or outflow ofcounterions in the conducting polymer known as “dopants”. Common dopantcounterions include ClO₄ ⁻ and BF₄ ⁻. As examples, the conductingpolymer poly(pyrrole) is dark blue and conductive in its oxidized(“doped” or “colored”) state and pale-green in its reduced (“de-doped”or “undoped”) state, and the conducting polymer poly(aniline) is nearlytransparent in its reduced state, transitioning to green or dark greenin its oxidized state. An electrochromic material is said to be“anodically coloring” if application of a positive voltage to it causesit to transition to a colored or dark state, and “cathodically coloring”if application of a negative voltage causes it to transition to acolored or dark state. Poly(pyrrole) and poly(aniline) are anodicallycoloring polymers.

The most convenient and common method of synthesis of conductingpolymers for electrochromic uses is electro-polymerization from asolution of the monomer directly onto a conductive, transparentsubstrate, such as indium-tin-oxide (ITO) on glass, poly(ethyleneterephthalate) (PET, “Mylar”) or other transparent plastic substrate.The electro-polymerization may be carried out using a constant appliedpotential (potentiostatic mode), a potential sweep (potential sweepmode) or other applied potential programs. Thus, e.g., poly(diphenylamine) may be electrochemically deposited onto ITO/glass or ITO/PET froma 0.05 M solution of the monomer in acetonitrile at about +0.8 V(potentiostatic mode).

A common transmissive-mode electrochromic device is fabricated bydepositing an electrochromic material on a conductive, transparentsubstrate, such as ITO/glass or ITO/PET, forming the active or workingelectrode. A similar substrate, ITO/glass, comprises the opposing orcounter electrode. A liquid, solid or gel electrolyte is disposed as alayer between the two electrodes or incorporated into the polymers. Theactive electrochromic material on the working electrode may be switchedto a dark “colored” or a less colored “bleached” state, depending on thevoltage applied to it in this 2-electrode device, thus modulating thetransmission through the device. A common reflective-mode electrochromicdevice may be fabricated in a similar fashion, with the difference that,in place of the transparent, conductive substrate, an opaque, conductivesubstrate, such as Au deposited on a microporous membrane, may be used.The counter electrode in such a device may be a similar conductivesubstrate disposed behind the working electrode. Such a reflective modedevice is described in U.S. Pat. No. 5,995,273 (1999) and U.S. Pat. No.6,033,592 (2000), issued to Chandrasekhar (collectively, the“Chandrasekhar IR patents”).

In the operation of such devices as described in the precedingparagraph, a voltage is applied to the working electrode. As an example,if the active electrochromic material thereon is anodically coloring,then a positive voltage will cause it to transition to a colored state.In the case of a conducting polymer, a corresponding inflow ofcounterions, in this case anions, will occur into the polymer.

In all 2-electrode electrochromic devices, at the same time that theworking electrode experiences a (+) voltage, the counter electrodeexperiences the identical (−) voltage, and vice versa. Anelectrochemical reaction will then need to occur at the counterelectrode to balance the charge transfer corresponding to the reactionoccurring at the working electrode; the availability of a suitablecounter electrode reaction is vital to the reversible functioning of theelectrochromic device. In the case where the counter electrode substrateis bare or naked, i.e. it does not have an electrochemically activematerial such as an electrochromic material deposited on it, the likelyelectrochemical reaction that occurs is reduction of impurities presentin the electrolyte, including, by way of example, dissolved gases(including oxygen); in the case of dissolved oxygen, species such as thesuperoxide ion or radical oxygen species may then be generated whichhave lifetimes as long as 20 seconds and which oxidatively orreductively degrade the active electrochromic material present on theother electrode (Menon et al., 1998) (Chandrasekhar IR patents,Chandrasekhar et al. 2002, Chandrasekhar et al. 1987). In such acircumstance, the overall electrochemical processes occurring within theelectrochromic device are said to exhibit poor reversibility. This leadsto a number of detrimental results, e.g. much more rapid degradation ofthe active electrochromic material and much slower electrochromicswitching time.

Anodically-Coloring Conducting Polymers

Anodically-coloring conducting polymers described include poly(aniline),poly(pyrrole) as well as the structurally related series comprisingpoly(diphenyl amine), poly(4-amino -biphenyl) (Dao and coworkers (Guayet al., 1988, 1989, LeClerc et al., 1988, Nguyen et al., 1990)) andpoly(N,N′-diphenyl benzidine) (Suzuki et al., U.S. Pat. No. 4,874,481(1989)). These polymers show a color transition from nearly transparentin their reduced state to dark blue or blue-green in their oxidizedstate, with modest but consistent light/dark contrast, Delta %-Transmission between light/dark states at 575 nm being ca. 40%.Furthermore, the voltages required for their switching are relativelylow, less than +1.5 V in many cases (in a 2-electrode-mode device with abare ITO/substrate electrode serving as the counter electrode). Anadditional, key advantage of this series of poly(aromatic amine)polymers is that they are nearly transparent or, in some cases,completely transparent in their fully reduced state.

These polymers do however show a number of drawbacks, the most importantof which is that, when incorporated into an electrochromic devicewithout the presence of a suitable, complimentary counter electrodereaction, they display very slow light/dark switching times (up to 25seconds) and modest contrast; they also then start to degrade afterabout 1000 cycles of light/dark switching. (Reasons for degradationinclude the lack of a counter-electrode reaction, resulting inimpurities or water/oxygen in the electrolyte undergoing redox at thecounter electrode; these may in turn generate harmful species, e.g. O₂^(.−), which further degrade the polymer). Nevertheless, thesepoly(aromatic amines) constitute an ideal set of anodically coloringelectrochromic polymers, if they could be paired with a well-performingset of cathodically coloring electrochromic polymers in a singleelectrochromic device.

Cathodically Coloring Electrochromic Conducting Polymers andStructure-Performance Relationships Therein

In terms of cathodically coloring electrochromic conducting polymers, anumber of these are described in the patent and journal literature. Oneof the first such polymers was poly(isothianaphthene) (first synthesizedby Wudl and coworkers (Hotta et al., 1987, Patil et al., 1987) and withsubsequent improvements in processing by Chandrasekhar et al., 1990),which transitions from a translucent blue-green in its oxidized state toa deep blue in its reduced state. Among its drawbacks was a relativelypoor light/dark contrast (Delta % T typically 20% at wavelength ofmaximum absorption), asymmetric switching voltages (+1.3 V fullyoxidized, −0.5 V fully reduced, all vs. Ag/AgC1), and rapid degradation(<200 cycles), i.e. poor “cyclability”.

A series of cathodically coloring polymers based onpoly(3,4-ethylenedioxythiophene) (PEDOT) and on other polymerscontaining the thiophene moiety have been described by Groenendal etal., (2000), Sapp et al. (1998), Gazotti et al. (1998) and others. Theseyield a variety of colors in their colored state, including yellow, red,blue and blue-black. Among their drawbacks are modest light/darkcontrast, large and asymmetric switching voltages, and modestcyclability. These polymers are generally not transparent in their lightstate, but rather lightly colored, semi-translucent, the colors varyingfrom undesirable reds, yellows and blues to desirable grays.

With respect to the search for better cathodically coloring polymers,then, the propylene analogues of PEDOT, derivatives ofpoly(3,4-propylenedioxythiophene) (PProDOT), show improvedelectrochromic performance over PEDOT derivatives. Welsh et al. (1999)describe a dimethyl-substituted derivative of PProDOT with highlight/dark contrast, with claimed Delta-% T ca. 65% at ca. 610 nm (thewavelength of highest absorption of the polymer); their Delta-% Tnumbers are however of electrochromic devices incorporating the polymerwhich are subtracted for the absorption of the substrates, i.e. theygive the absorption due to the polymer alone, with the substrates ratherthan air used as reference; based on the expected absorptions for thesubstrates they use, the Delta-% T for the dimethyl-substituted PProDOTis closer to 38% for the actual device against air (rather thansubstrate) reference. Nevertheless, Welsh et al. demonstrate, in acomparison of the electrochromic properties of the dimethyl-PProDOT withthe unsubstituted PProDOT that the substitution, in this case 2,2′dimethyl substitution, on the propylene of the ProDOT monomer yieldssignificant improvement of the electrochromic properties of theresulting polymer, such as improved light/dark contrast and a lower andmore symmetric switching voltage (in the case of dimethyl-PProDOT, aconvenient ca. +/−1.0 V).

Krishnamoorthy et al. disclose dibenzyl-substituted derivatives ofPProDOT, which are also cathodically coloring conducting polymers; theseappear to the best reported electrochromic performance to date forcathodically coloring conducting polymers, although again, the data arequoted vs. substrate rather than air reference so actual performancemust only be estimated. The wavelength of highest absorbance of thispolymer in its dark state is ca. 630 nm. Switching times of <5 secondsare reported. An advantageous feature of this polymer is that, like itsdimethyl-substituted analog (Welsh et al., 1999, discussed above), itswitches at low, symmetrical voltages, about +/−1.0 V. This dibenzylPProDOT (“P(DiBz-ProDOT)”) thus appears to be very well suited for useas the cathodically coloring counterpart in a complimentary-polymerelectrochromic device also incorporating a well-performing anodicallycoloring polymer. Its wavelength of highest absorbance (630 nm) is alittle on the higher wavelength side, close to the near-IR; if thiscould be shifted to near 550 nm, more towards the green, perhaps by afortuitous substitution on the benzyl ring, it would constitute an idealcathodically-coloring polymer.

Complimentary Electrode (e.g. Dual Polymer) Electrochromic Devices

Electrochromic devices incorporating complimentarily-coloring (i.e.,anodically and cathodically coloring) electrochromic materials may showimproved performance over devices containing a single (either anodicallyor cathodically coloring) electrochromic material. Set forth here noware examples of such improved performance in actually reported data todate.

For example, a complimentary electrochromic device based onpoly(o-methoxyaniline) doped with p-toluene sulfonic acid (PoANis-TSA)as the anodically coloring polymer and a blend ofpoly(4,4′-dipentoxy-2,2′-bithiophene) (PET2) andpoly(epichlorohydrin-co-ethylene oxide) (Hydrin-C) is described in apublication of Gazotti et al. (1998). In this device, moderatelight/dark contrast, Delta % T=32% at 620 nm (though again vs. asubstrate reference rather than an air reference) is coupled with veryfast switching time, <2 seconds, as is to be expected for such acomplimentary polymer device based on the discussion above. As anotherexample, complimentary polymer devices based on co-polymers ofethylene-dioxythiophene derivatives with N-methylcarbazole are describedin a publication of Sapp et al. In this work, twelve complimentarypolymer pairs are studied, all having EDOT derivatives as thecathodically coloring component. The best switching time reported inthis work is ca. 3 seconds and the best light/dark contrast, Delta-% T,of 63% at 650 nm, the wavelength of highest absorbance (although this isagain with device substrate rather than air as reference): A correctionfor the substrate absorption yields a corrected Delta-% T of 40% (vs.63% uncorrected). Additionally, the very high wavelength of highestabsorption (650 nm, in the red and close to the near-IR boundary) andthe narrow rather than broad-band nature of the absorption is a seriousdrawback of the best of these 12 complimentary-polymer devices. Inanother example, Groenendal et al. claim light/dark contrasts as high as45% at 620 nm for one P(EDOT) polymer in a complimentary polymer device;again, however, these values represent substrate-subtracted spectra, andactual contrasts (i.e. against air reference) are closer to 30% for thispolymer.

In yet another example of complimentary-electrochromic devices U.S. Pat.No. 6,859,297 (2005), issued to Lee et al., discloses an amorphous,anodically coloring electrochromic material comprising nickel oxidedoped with tantalum. This material is deposited on a transparent,conductive substrate. Notably, it is coupled with a cathodicallycoloring material, such as electrochromic material based on tungstenoxide, yielding a complimentary-electrochromic device havingcathodically and anodically electrochromic materials in the same device.The composite device is shown to be significantly superior inperformance to single-electrochromic (either cathodically or anodicallycoloring) devices.

The complimentary-polymer electrochromic devices and systems discussedabove however, have very significant drawbacks. The first of thesedrawbacks is that the complimentary polymers are not well matched interms of the potential at which they undergo oxidation/reduction. As anexample, in its cyclic voltammogram, the cathodically-coloringpoly(isothianapthene) shows two sharp oxidation peaks between +0.5 and+1.2 V, a reduction peak at ca. +0.8 V, and another reduction peak atca. +0.4 V, all vs. Ag/AgC1 (Chandrasekhar, 1990). In comparison, theanodically-coloring poly(diphenyl amine) and poly(4-amino-biphenyl) bothshow oxidation peaks at ca. +0.5 V and ca. +0.8 V and reduction peaks atca. +0.8 V and +0.5 V (all vs. Ag/AgC1) (Guay et al. 1989). Similarly,the anodically-coloring poly(N,N′-diphenyl benzidine) shows a singleoxidation peak at ca. +1.4 V and a single reduction peak at ca. 0.0 V(all vs. Ag/AgC1) (Chandrasekhar et al., 1991). Thus, even with a smallshift expected in dual-polymer devices, these anodically-coloringpolymers would make a very poor match for the cathodically-coloringpoly(isothianaphthene). When the anodically coloring polymer of the pairis fully oxidized at the most extreme (+) voltage usable for the pair,the cathodically coloring polymer may only be partially reduced and sonot able to contribute fully to the electrochromic contrast. Indeed,such a “mismatch” situation for most prior-art cathodically-coloring andanodically-coloring polymers may be demonstrated by experiment.

A second drawback of these complimentary-polymer systems is that nearlyall of the cathodically-coloring polymers used do not themselves (i.e.on their own, in single-polymer devices) show significant light/darkcontrast; they also frequently show narrow-band absorption. On the rareoccasions that a high-contrast cathodically coloring polymer, such asthe dibenzyl-PProDOT (P(DiBz-ProDOT)) referenced above, has been used ina complimentary polymer device, it has been paired with poorly matchedanodic conducting polymers which also display mediocre electrochromicperformance. See, e.g., Invernale et al. (2009) and Padilla et al.(2007). Additionally, nearly all cathodically-coloring polymers used insuch devices are not transparent in their light state, but rathertranslucent, with significant, sometimes undesirable (e.g. light greenor blue) coloration. Yet further, except in rare cases such as theP(DiBz-ProDOT) cited above, cathodically-coloring polymers used incomplimentary devices to date generally have narrow band absorptionwhich is frequently in the red region, with the wavelength of highestabsorption generally in the 620 to 650 nm range.

A third drawback of these prior art complimentary-polymer systems,related to the first two, is that the redox reactions of the pair arenot matched in terms of number of electrons involved. For example in thecited study of Sapp et al. (1998), the anodically coloring redoxreaction in many of the pairs studied is a 2-electron reaction whilstthe cathodically coloring reaction is a 1-electron reaction. Such amismatch generates significant overpotential which reduces theelectrochromic efficiency of the device.

Accordingly, there is a significant need in the art for dual-polymerdevices that are capable of overcoming the aforementioned deficiencies.

SUMMARY OF THE INVENTION

In general terms, the present invention provides dual-polymerelectrochromic devices which overcome the drawbacks of prior-artdual-polymer devices, as described at length in the discussion above.Moreover, the present invention provides novel cathodically-coloringpolymers especially suitable for such dual-polymer devices. Indeed, thepresent invention provides cathodically-coloring polymers that are wellmatched electrochromically and electrochemically to appropriateanodically-coloring polymers, as described in more detail below.

In a first embodiment, the present invention provides a complimentaryelectrochromic device comprising:

(a) a first electrode comprising a cathodically coloring conductingpolymeric material, the cathodically coloring conducting polymericmaterial comprising a substituted or unsubstituted2,2-dibenzyl-3,4-propylenedioxythiophene monomer;

(b) a second electrode comprising an anodically coloring conductingpolymeric material;

(c) an electrolyte disposed between and in electrochemical communicationwith the first electrode and the second electrode; and

wherein the redox potential of the cathodically coloring conductingpolymeric material is substantially matched to the redox potential ofthe anodically coloring conducting polymeric material such that when onesaid polymeric material is fully oxidized, the other said polymericmaterial is fully reduced.

In one aspect of the device, at least one benzyl moiety of thesubstituted 2,2-dibenzyl-3,4-propylenedioxythiophene is para substitutedwith a substituent selected from the group consisting of halo, sulfonyl,nitro, and alkyl. In preferred aspects, the benzyl moiety of thesubstituted 2,2-dibenzyl-3,4-propylenedioxythiophene is substituted witha chloro or bromo substituent.

In another aspect of the device, the cathodically coloring conductingpolymeric material may comprise a copolymer. In a further aspect, thepolymeric material may comprisepoly(2,2-dibenzyl-3,4-propylenedioxythiophene),poly(2,2-bis(4-chloro-benzyl)-3,4-propylenedioxythiophene),poly(2,2-bis(4-bromo-benzyl)-3,4-propylenedioxythiophene),poly(2,2-bis(4-nitro-benzyl)-3,4-propylenedioxythiophene), orcombinations thereof. In yet another aspect, the cathodically coloringconducting polymeric material may comprise at least one monomer selectedfrom the group consisting of2,2-bis(4-chloro-benzyl)-3,4-propylenedioxythiophene,2,2-bis(4-bromo-benzyl)-3,4-propylenedioxythiophene), and combinationsthereof. In another aspect the cathodically conducting polymericmaterial may comprise a copolymer of the monomers2,2-dibenzyl-3,4-propylenedioxythiophene,2,2-bis(4-chloro-benzyl)-3,4-propylenedioxythiophene), and2,2-bis(4-bromo-benzyl)-3,4-propylenedioxythiophene). Additionally, thecathodically conducting polymeric material may comprise a copolymer ofthe monomers 2,2-dibenzyl-3,4-propylenedioxythiophene,2,2-bis(4-chloro-benzyl)-3,4-propylenedioxythiophene), and2,2-bis(4-bromo-benzyl)-3,4-propylenedioxythiophene), in a molar ratioin the range of 1:1:1 to 50:7:1, respectively.

In a still further aspect of the device, the anodically coloringconducting polymeric material may comprise a poly(aromatic amine). Inother aspects, the anodically conducting polymeric material comprises acopolymer. In preferred aspects, the anodically conducting polymermaterial may comprise at least one monomer selected from the groupconsisting of N,N′-diphenyl benzidine, diphenyl amine, 4-aminobiphenyl,and combinations thereof. In a more preferred aspect, the anodicallycoloring conducting polymeric material comprises a copolymer of themonomers N,N′-diphenyl benzidine, diphenyl amine and 4-aminobiphenyl ina molar ratio in the range of 1:1:1 to 50:1:1, respectively.

In other aspects of the device, the first and/or second electrodecomprises a first and/or second conductive transparent substrate. Inanother aspect, the first and/or second conductive substrate maycomprise indium-tin-oxide(ITO)/glass, ITO/poly(ethyleneterephthalate)(PET), tin-oxide/glass, tin-oxide/PET, gold/glass,carbon-nanotubes/glass, carbon-nanotubes/PET, gold/PET, or a combinationthereof. Additionally, in some aspects of the device, the electrolytemay comprise a liquid electrolyte, solid electrolyte, gel electrolyte,or a combination thereof.

In another embodiment, the instant invention encompasses a method forobtaining a complimentary electrochromic device comprising the steps of:

(a) preparing a first electrode by depositing a cathodically coloringconducting polymeric material on a first transparent conductivesubstrate to obtain the first electrode, wherein the cathodicallycoloring conducting polymeric material comprises a substituted orunsubstituted 2,2-dibenzyl-3,4-propylenedioxythiophene monomer;

(b) preparing a second electrode by depositing an anodically coloringconductive polymeric material on a second transparent conductivesubstrate to obtain the second electrode, wherein the anodicallycoloring conductive polymer material comprises a poly(aromatic amine);

(c) superimposing the first electrode and the second electrode andproviding a space between the first and second electrodes; and

(d) placing an electrolyte in the space between the first and secondelectrodes to provide the electrochromic device, wherein the electrolyteis in electrochemical communication with the first and secondelectrodes.

In further embodiments, the invention provides a compound of theformula:

wherein X is an electron-withdrawing substituent. In certain aspects, Xis a substituent selected from the group consisting of cyano, sulfoxy,carboxy, carboxylate, aldehyde, carbonyl, halo, alkyl, sulfonyl, nitro,and amino.

In another embodiment, the present invention provides a method forpreparing 2,2-bis(4-X-benzyl)-3,4-propylenedioxythiophene, wherein X isa substituent selected from the group consisting of halo, alkyl,sulfonyl, nitro, and amino, comprising the steps of reacting the2,2-bis(4-X-benzyl)-3,4-propanediol with 3,4-dimethoxythiophene underconditions effective to yield2,2-bis(4-X-benzyl)-3,4-propylenedioxythiophene. In other embodiments,the instant invention provides a substituted dibenzyl 1,3-propanediolwherein the para position of at least one benzyl moiety is substitutedwith a substituent selected from the group consisting of halo, sulfonyl,nitro, amino, and alkyl, and a method of preparing the same.

In still another embodiment, the present invention provides a method forpreparing an electrode, comprising the steps of:

(a) providing a deposition solution comprising at least one monomer of acathodically coloring polymeric material, wherein the at least onemonomer comprises 2,2-bis(4-X-benzyl)-3,4-propylenedioxythiophene,wherein X is a substituent selected from the group consisting of halo,alkyl, sulfonyl, and nitro; and

(b) uniformly depositing the cathodically coloring conducting polymermaterial onto a transparent conductive substrate to provide theelectrode.

In an additional embodiment, the present invention provides a method forpreparing an electrode, wherein the electrode comprises a polymer ofN,N′-diphenyl benzidine monomer, the method comprising the steps of:

(a) providing a deposition solution comprising the N,N′-diphenylbenzidine monomer;

(b) uniformly depositing the polymeric material onto a substrate incontact with the deposition solution to yield the electrode; and

wherein the deposition solution comprises dimethylformamide andacetonitrile in a ratio of at least about 6:1 by volume, respectively.

DESCRIPTION OF THE DRAWINGS AND FIGURES

The following description will be more easily understood when read inconjunction with the accompanying figures in which:

FIG. 1 shows cross-sectional and top views of the complimentary polymer(“dual-polymer”) electrochromic device according to the presentinvention.

FIG. 2 is a representation of the chemical structures of the variousmonomers and other relevant moieties as described in the presentinvention.

FIG. 3 shows the synthetic scheme as used by Krishnamoorthy et al. forsynthesis of the monomer 2,2-dibenzyl-ProDOT(2,2-dibenzyl-propylene-dioxythiophene, “Bz-ProDOT”).

FIG. 4 shows the synthetic scheme for synthesis of the monomer2,2-(bis-4-chlorobenzyl)-3,4-propylenedioxythiophene (also called“3,3-Bis(4-chlorobenzyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]-dioxepine” or“Cl-Bz-ProDOT”), according to the present invention.

FIG. 5 shows the synthetic scheme for synthesis of the monomer2,2-(bis-4-bromobenzyl)-3,4-propylenedioxythiophene (also called“3,3-Bis(4-bromobenzyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]-dioxepine” or“Br-Bz-ProDOT”), according to the present invention.

FIG. 6 shows the synthetic scheme for synthesis of the monomer2,2-(bis-4-nitrobenzyl)-3,4-propylenedioxythiophene (also called“3,3-Bis(4-nitrobenzyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]-dioxepine” or“Nitro-Bz-ProDOT, according to the present invention.

FIG. 7 shows the synthetic scheme for synthesis of the monomer2,2-(bis-4-aminobenzyl)-3,4-propylenedioxythiophene(“3,3-Bis(4-aminobenzyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]-dioxepine” or“Amino-Bz-ProDOT”), according to the present invention

FIG. 8 shows cyclic voltammograms of the electrochromic device asassembled in COMPARATIVE EXAMPLE 16, wherein poly(isothianaphthene)(PITN) is the cathodically-coloring polymer and a copolymer ofN,N′-diphenyl benzidine, diphenyl amine and 4-amino-biphenyl is theanodically-coloring polymer, between the voltages corresponding to itsextreme light and dark states.

FIG. 9 shows the UV-Vis-NIR spectra of the electrochromic device asassembled in COMPARATIVE EXAMPLE 16, wherein PITN is thecathodically-coloring polymer and a copolymer of N,N′-diphenylbenzidine, diphenyl amine and 4-amino-biphenyl is theanodically-coloring polymer, in its extreme light and dark states.

FIG. 10 shows the UV-Vis-NIR spectra of the electrochromic deviceassembles as in COMPARATIVE EXAMPLE 17, demonstrates a single-polymerelectrochromic device comprising poly(N,N′-diphenyl benzidine), in itsextreme light and dark states.

FIG. 11 comparatively shows the UV-Vis-NIR spectra in the extremelight/dark states of two electrochromic devices: (1) A device assembledaccording to COMPARATIVE EXAMPLE 15, whereinpoly(2,2-(bis-4-chloro-benzyl)-3,4-propylenedioxythiophene)(“Poly(Cl-Bz-ProDOT)”) is the cathodically coloring polymer and acopolymer of N,N′-diphenyl benzidine, diphenyl amine and4-amino-biphenyl is the anodically coloring polymer. (2) A deviceassembled according to EXAMPLE 14, wherein a copolymer of2,2-(bis-4-chloro-benzyl)-3,4-propylenedioxythiophene,2,2-(bis-4-bromo-benzyl)-3,4-propylenedioxythiophene and2,2dibenzyl-3,4-propylenedioxythiophen is the cathodically-coloringpolymer and a copolymer of N,N′-diphenyl benzidine, diphenyl amine and4-amino-biphenyl is the anodically-coloring polymer.

FIG. 12 shows the corresponding switching time data for the same devicesas seen in FIG. 11.

FIG. 13 comparatively shows cyclic voltammetric data for: (1) Asingle-polymer, cathodically-coloring electrode having a copolymer of2,2-(bis-4-chloro-benzyl)-3,4-propylenedioxythiophene,2,2-(bis-4-bromo-benzyl)-3,4-propylenedioxythiophene and2,2-dibenzyl-3,4-propylenedioxythiophene as the polymer. (2) Asingle-polymer, anodically-coloring device having a copolymer ofN,N′-diphenyl benzidine, diphenyl amine and 4-amino-biphenyl as thepolymer. (3) A composite, dual-polymer device incorporating these twoindividual polymers.

FIG. 14 shows cyclic voltammetric data for: (1) A dual polymer device inwhich the cathodically-coloring polymer ispoly(2,2-(bis-4-chloro-benzyl)-3,4-propylenedioxythiophene) and theanodically coloring polymer is a copolymer of N,N′-diphenyl benzidine,diphenyl amine and 4-amino-biphenyl. (2) A dual polymer device in whichthe cathodically-coloring polymer is a copolymer of2,2-(bis-4-chloro-benzyl)-3,4-propylenedioxythiophene,2,2-(bis-4-bromo-benzyl)-3,4-propylenedioxythiophene and2,2-dibenzyl-3,4-propylenedioxythiophene. The total charge depositedduring the polymerizations of the cathodically-coloring polymers in bothdevices were nearly identical, as were those for the anodically-coloringpolymers in both devices.

FIG. 15 shows the UV-Vis-NIR spectra in the extreme light/dark states ofthe device assembled according to EXAMPLE 14, wherein a copolymer of2,2-(bis-4-chloro-benzyl)-3,4-propylenedioxythiophene,2,2-(bis-4-bromo-benzyl)-3,4-propylenedioxythiophene and2,2-dibenzyl-3,4-propylenedioxythiophene is the cathodically-coloringpolymer and a copolymer of N,N′-diphenyl benzidine, diphenyl amine and4-bromo-biphenyl is the anodically-coloring polymer, but with thedifference that the total charge deposited for both the cathodically-and anodically-coloring polymers was ca. 17% greater.

DETAILED DESCRIPTION OF THE INVENTION

While the compositions, methods and devices heretofore are susceptibleto various modifications and alternative forms, exemplary embodimentswill herein be described in detail. It should be understood, however,that there is no intent to limit the invention to the particular formsdisclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the invention as defined by the appended claims.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe relevant art. Although any methods and materials similar orequivalent to those described herein can also be used, the preferredmethods and materials are now described.

Where an electrochemically active material possessing highly reversibleelectrochemical activity is introduced on a counter electrode it may beconfigured to act in a complimentary and highly reversible fashion tothe material at a working electrode. For example, when theelectrochromic material at the working electrode undergoes oxidation,the complimentary material at the counter electrode would undergoreduction, and vice versa. This leads to a highly reversibleelectrochemical system where the active electrochromic displays muchmore rapid switching times, higher light/dark contrast, highlyreversible switching and little degradation over a very large number ofswitching cycles. This is the principle behind complimentarily coloringelectrochromic devices.

The simplest and most efficient of such complimentarily coloring deviceis one in which the same electrochromic material is disposed on both theworking and counter electrode. Such a system, where the electrochromicon one electrode undergoes a redox process “equal and opposite” to thatat the other electrode, is by definition highly reversible. Such asystem would work well for a reflective-mode electrochromic device.However, it would be useless for a transmissive-mode (see-through)device, since the overall device would not change color at all: Oneelectrode's darkness would compensate for the other electrode'slightness. However, if one of the electrochromic materials showsactivity that is opposite to that of the other, e.g. it turns to itslight state on application of a (+) voltage while the other materialturns dark on application of a (+) voltage, then this would yield afunctioning transmissive-mode, complimentarily-coloring device.Furthermore, if the two materials were ideally matched, so that at theapplied voltage at which one is in its darkest state, the other is atits lightest state, this would then constitute an idealcomplimentary-coloring, transmissive-mode electrochromic system.

In the present invention a complimentary polymer or “dual-polymer”electrochromic device is provided having electrodes and comprising ananodically-coloring conductive polymeric material, an electrolyte layer,and a cathodically coloring conductive polymeric material. As usedherein, a “coloring conductive polymeric material” is said to be“anodically coloring” if application of a positive voltage to it causesit to transition to a colored or dark state, and “cathodically coloring”if application of a negative voltage causes it to transition to acolored or dark state. Moreover, cathodically and anodically coloringconductive polymeric materials comprise cathodically and anodicallycoloring polymers, respectively.

As used herein, the term “polymer” refers to the product of apolymerization reaction, and is inclusive of homopolymers, copolymers,terpolymers, etc.

As used herein, the term “homopolymer” is used with reference to apolymer resulting from the polymerization of a single monomer, i.e., apolymer consisting essentially of a single type of repeating unit.

As used herein, the term “copolymer” refers to polymers formed by thepolymerization reaction of at least two different monomers and,moreover, the term copolymer is inclusive of random copolymers, blockcopolymers, graft copolymers, etc.

The cathodically coloring conductive polymeric material of the inventionmay comprise one or more polymers that comprise an unsubstituted orsubstituted derivative of 2,2-dibenzyl-3,4-propylene-dioxythiophenemonomer. Preferably, when the 2,2-dibenzyl-3,4-propylene-dioxythiopheneis substituted, the substitution may be located at the para position ofthe benzyl group, wherein the substituents at the benzyl moiety may behalo (e.g., chloro, bromo, iodo, fluoro), sulfonyl, nitro, amino oralkyl (e.g., n-propyl, iso-propyl, n-butyl, iso-butyl, n -pentyl,n-hexyl) substituents.

Preferably, the cathodically coloring polymer is a copolymer of monomersbased on a 3,4-propylenedioxythiophene skeleton. Examples of suchmonomers include, but are not limited to,2,2-bis(4-chlorobenzyl)-3,4-propylenedioxythiophene,2,2-bis(4-bromobenzyl)-3,4-propylenedioxythiophene,2,2-bis(4-nitrobenzyl)-3,4-propylenedioxythiophene,2,2-bis(4-aminobenzyl)-3,4-propylenedioxythiophene and2,2-dibenzyl-1,3-propylenedioxythiophene.

More preferably, the cathodically coloring conducting polymer is acopolymer of the monomers 2,2-dibenzyl-3,4-propylenedioxythiophene,2,2-bis(4-chlorobenzyl)-3,4-propylenedioxythiophene, and2,2-bis(4-bromobenzyl)-3,4-propylenedioxythiophene, taken in a molarratio of about 1:1:1 to 50:1:1, reflecting the variation of the firstmonomer's proportion, and again from 50:1:1 to 50:7:1 and 1:1:1 to1:7:1, reflecting the variation of the second monomer's proportion. Morepreferably, the above molar ratio is 50:1:1 to 3:1:1. More preferablystill, the above molar ratio is 20:1:1 to 3:1:1. Most preferably, theabove molar ratio is about 10:1:1. The electrochromic performance ofelectrochromic devices containing these copolymer systems is seen to besuperior to that of devices having only pure polymers of these monomers.

Anodically coloring conducting polymeric materials of the invention maycomprise one or more polymers or, more preferably, may be a copolymer ofmonomers known in the art which include but are not limited topoly(aromatic amine) polymers. Examples of such monomers include, butare not limited to, diphenyl amine, N,N′-diphenyl benzidine,4-aminobiphenyl and aniline. The anodically coloring polymer ispreferably a copolymer of monomers N,N′-diphenyl benzidine, diphenylamine and 4-aminobiphenyl taken in a molar ratio of about 1:1:1 to50:1:1, with electrochromic performance seen to be superior to that ofthe pure polymers of these monomers. Preferably, the above molar ratiois from about 1:1:1 to about 20:1:1. More preferably, the above molarratio is from about 1:1:1 to about 9:1:1 and even more preferably, theabove molar ratio is about 3:1:1 to 7:1:1. In an especially preferredembodiment, the above molar ratio is about 5:1:1.

Preferably, the cathodically and anodically coloring conductive polymersof the complimentary-polymer electrochromic device of the presentinvention are electrochromically and electrochemically matched. As usedherein, the redox potentials of the cathodically coloring polymericmaterial and anodically coloring polymeric material in a 2-electrodeelectrochromic device are considered “substantially matched” when, at agiven potential, the cathodically coloring polymeric material is fullyoxidized and the anodically coloring polymeric material is fullyreduced, and vice versa. More particularly, the cathodically andanodically coloring polymeric materials are considered “substantiallymatched” when the cathodically and anodically coloring polymericmaterials both show at least about 85%, about 90%, or about 95% of theirtotal charge transferred corresponding to their electrochromicallyrelevant oxidation or reduction peaks, at a given potential, asdetermined by examining the area under the curve of the cathodically andanodically coloring polymeric material's individual voltammetric peaks.

Accordingly, where the cathodically and anodically coloring polymericmaterials have substantially matched redox potentials, upon applicationof the (−) potential where the cathodically coloring polymeric materialis at its darkest state, the anodically coloring polymeric material isat its lightest state; and, upon application of the (+) potential wherethe anodically coloring polymeric material is at its darkest state, thecathodically coloring polymeric material is at its lightest state.

Due to this good matching of the electrochemical redox potentials andthe electrochromic properties of the complimentary polymers, thedual-polymer devices display electrochromic performance superior to thatof the single-polymer devices as well as to prior art dual-polymerdevices wherein either the cathodically-coloring or anodically-coloringpolymer are different from the above listed polymers and are notelectrochromically and electrochemically matched as described above.(Electrochromic performance is described by light/dark contrast,switching speed, cyclability, and related parameters).

In providing the dual-polymer devices of the present invention, thecathodically and anodically coloring polymeric materials may be composedof homopolymers. In preferred embodiments at least one of thecathodically coloring polymeric material and anodically coloringpolymeric material may be composed of a copolymer. Most preferably, boththe cathodically and anodically coloring polymeric materials arecomposed of copolymers. The anodically and cathodically coloringpolymeric materials may be deposited on transparent conductivesubstrates which may form opposing electrodes in an electrochromicdevice with a thin layer (preferably a thin layer) of liquid, gel orsolid electrolyte disposed between them. The device may further comprisea means (e.g. gasket) for sealing and containing said electrolyte withinthe device.

Additionally, methods are provided for assembling and preparingelectrochromic devices which may utilize a deposition solution. Thedeposition solution used in the device and methods set forth maycomprise (A) (1) for depositing a cathodically coloring polymer, (i) a2,2-bis(benzyl)-3,4-propylenedioxythiophene derivative substituted atthe para position of at least one benzyl group with a halo, sulfonyl,nitro or alkyl moiety and optionally (ii)2,2-dibenzyl-3,4-propylenedioxythiophene; OR (2) for depositing ananodically coloring polymer, monomers N,N′-diphenyl benzidine, diphenylamine and/or 4-aminobiphenyl; (b) a salt containing a counterion that isultimately incorporated as the dopant in the polymer or copolymerdeposited onto an electrode and (c) a solvent. The deposition solutionmay be obtained by combining a2,2-bis(benzyl)-3,4-propylenedioxythiophene substituted at the paraposition of at least one benzyl group with a halo, sulfonyl, nitro oralkyl moiety and optionally 2,2-dibenzyl-3,4-propylenedioxythiophenewith one or more salts in a solvent.

Salts that may be used in the deposition solution include but are notlimited to Na⁺, Li⁺, Et₄N⁺ as cations and poly(vinylsulfonate), sulfate,trifluoromethane sulfonate and poly(styrene sulfonate) as anions.Solvents that may be used include but are not limited to acetonitrile,N,N′ dimethyl formamide (DMF), tetrahydrofuran (THF) and mixturesthereof. The polymer may be deposited from the deposition solution ontosaid transparent conductive substrate using a multiple potential sweepmethod, or a potential step (constant potential) method. More preferablyfor the cathodically coloring polymers, it may be deposited with apotential sweep method, with the potential from about 0.0 V to about+1.5V.

Cathodically-Coloring Polymer

The cathodically-coloring polymer comprises substituted andunsubstituted derivatives ofpoly(2,2-dibenzyl-3,4-propylenedioxythiophene) (“DiBz-PProDOT”). Inparticular reference to the substituted Dibenzyl-PProDOT, in a preferredembodiment, at least one benzyl moiety is substituted with an amino,nitro, halo, sulfonyl or alkyl group (e.g., propyl, isopropyl, n -butyl,iso-butyl, n-pentyl, n-hexyl). As used herein, “halo,” may be defined ascomprising fluoro, chloro, bromo and iodo substituents. In aparticularly preferred embodiment, the para position of the benzyl groupis substituted.

In a preferred embodiments, the cathodically-coloring polymers exhibitlarge electrochromic contrast and electrochemical and electrochromiccompatibility with anodically -coloring polymers. DiBz-PProDOT polymerswith dichloro- or other substituents at the para-position of each of thebenzyl groups, may exhibit very significant improvement inelectrochromic properties over theirunsubstituted-dibenzyl-counterparts. In particular, with thesubstitution at the dibenzyl group, the polymer absorption may changesuch that it is more broad -band; additionally, the wavelength ofhighest absorption may also shift, potentially more towards the centerof the visible spectral region (ca. 575 nm), and again, potentially, theswitching voltages may be slightly lowered and made more symmetrical.Other possible changes of the substitution at the dibenzyl group couldbe a significant increase in the absorption, leading to a much higherlight/dark contrast, and a shift in the redox potential, leading,potentially, to a much better match with anodically-coloring polymerssuch as poly(aromatic amines) in a dual-polymer device. Production ofthese polymers is achieved via electro-polymerization from thesubstituted-dibenzyl monomer, according to established conductingpolymer electrochromics practice.

In another particular embodiment, the polymer may comprise a copolymerof derivatives of poly(2,2-dibenzyl-3,4-propylenedioxythiophene)substituted at the para position of the benzyl moiety. In particularlypreferred embodiments, the monomer components may include2,2-dibenzyl-3,4-propylenedioxythiophene, a derivative of2,2-dibenzyl-3,4-propylenedioxythiophene substituted at the paraposition of the benzyl moiety with a chloro substituent and optionally aderivative of 2,2-dibenzyl-3,4-propylenedioxythiophene substituted atthe para position of the benzyl moiety with a bromo substituent.

A particular cathodically coloring polymer composition of the inventionis a copolymer of the monomers 2,2-dibenzyl-3,4-propylenedioxythiophene,2,2-bis(4-chloro-benzyl)-3,4-propylenedioxythiophene, and2,2-bis(4-bromo-benzyl)-3,4-propylenedioxythiophene, taken in a molarratio of about 1:1:1 to 50:1:1, reflecting the variation of the firstmonomer's proportion, and again from 50:1:1 to 50:7:1 and 1:1:1 to1:7:1, reflecting the variation of the second monomer's proportion. Theelectrochromic performance of electrochromic devices containing thesecopolymer systems is seen to be superior to that of devices having onlypure polymers of these monomers. More preferably, the above molar ratiois 50:1:1 to 3:1:1. More preferably still, the above molar ratio is20:1:1 to 3:1:1. Most preferably, the above molar ratio is about 10:1:1.

Synthesis of Monomer Precursors of High-Performance CathodicallyColoring Polymers

The monomers used, particularly the derivatives set forth above may beobtained by providing a 2,2-dibenzyl-1,3-propanediol substituted at the4-position (i.e., para position) of the benzyl group with the desiredsubstituent (such as but not limited to the halo, alkyl, sulfonyl ornitro group). It is further noted that the p-bromo-substituted2,2-bis(benzyl)-3,4-propylenedioxythiophene is particularly valuable asan intermediate in the further synthesis of monomer derivatives of2,2-bis(benzyl)-3,4-propylenedioxythiophene with other substituents atthe p-position of the benzyl group through common synthetic organicchemical techniques known to anyone skilled in the art. The1,3-propanediol may be obtained by reducing a 2,2-dibenzyl-malonatesubstituted at the 4 position of the benzyl group with the desiredsubstituent (such as but not limited to the halo, alkyl, sulfonyl ornitro group). Examples of various malonates that may be used and methodsof synthesis are set forth in the text below and in the EXAMPLES.

The 2,2-bis(benzyl)-1,3-propanediol substituted at the 4 position of thebenzyl group with the desired substituent (such as but not limited tothe halo, sulfonyl or nitro group) is reacted with1,3-dimethoxythiophene in a transesterification reaction facilitated by,for example, p-toluene sulfonic acid to yield the monomer,bis(4-substituted-benzyl)-3,4-propylenedioxythiophene.

This synthetic task is not entirely trivial. Krishnamoorthy et al.synthesized dibenzyl -PProDOT using a transesterification reactionbetween 3,4-dimethoxy-thiophene and 2,2-dibenzyl-propane-1,3-diol (asseen in the scheme in FIG. 3). The latter in turn was synthesizedstarting with diethyl malonate and reacting it with benzyl chloride toyield 2,2-dibenzyl -diethyl malonate using a strong base (sodiumethoxide in ethanol medium). The 2,2-dibenzyl-diethyl malonate was inturn reduced to yield the 2,2-dibenzyl-propane-1,3-diol using a standardlithium-aluminum-hydride reduction.

While diethyl malonate may react in a straightforward manner with benzylchloride, facilitated by the strong base sodium ethoxide, the samecannot be said for the p-substituted benzyl chlorides, e.g. thep-chloro-substituted benzyl chloride. In fact, the reaction in sodiumethoxide medium fails, as does the reaction with other base mediacommonly used in organic synthesis, such as triethyl amine anddi-isopropylethyl amine (see COMPARATIVE EXAMPLES). It thus appears thatthe availability of the para position on the benzyl rings is requiredfor the success of this reaction with common organic bases, and when itis blocked, the reaction fails. This is illustrated in a comparison ofsyntheses of the monomer2,2-bis(4-chlorobenzyl)-3,4-propylenedioxythiophene) (“Cl-Bz-ProDOT)described in EXAMPLE 1 (the successful synthesis using the base andreaction conditions of choice, involving steps through the intermediatesdiethyl-bis(4-Cl-benzyl) malonate and 2,2-bis(4-chlorobenzyl)-propanediol) versus COMPARATIVE EXAMPLES 2, 3 and 4 (unsuccessfulsyntheses using bases commonly used in organic synthesis for synthesisof the 1st intermediate above, diethyl-bis(4-Cl -benzyl) malonate).

Another subject of the present invention, therefore, is the successfulsynthesis of the precursors required to synthesize the p-dichloro-,p-dibromo and p-dinitro-substituted dibenzyl PPro-DOT electrochromicpolymers, specifically, 2,2-bis(4-chloro-benzyl)-1,3-propanediol,2,2-bis(4-bromo-benzyl)-1,3-propanediol, and2,2-bis(4-nitro-benzyl)-1,3-propanediol. Typical syntheses are describedin EXAMPLES 1, 5 and 6.

Synthesis of the monomer,2,2′-(bis-4-nitrobenzyl)-3,4-propylenedioxythiophene (“NO²-Bz-ProDOT”),i.e. the nitro-substituted analog of the chloro-substituted monomerdescribed above, starts with 4-nitrobenzyl bromide and includes a seriesof steps which involve use of protective groups, as described at lengthin EXAMPLE 6, which also reference the relevant reaction schemesrepresented in the FIGURES.

EXAMPLE 8 describes a typical electrochemical deposition (i.e.,polymerization) of the polymer,poly(2,2-bis(4-chloro-benzyl)-3,4-propylenedioxythiophene)(“poly(Cl-Bz-ProDOT)”) from monomer solution.

The polymer is preferably deposited from a nonaqueous monomer solution.A potential sweep method is preferably used. A potentiostatic (constantpotential) method yields poorly formed, inhomogeneous polymer films withpoor electrochromic performance and with a tendency to crack. Morepreferably, a multiple potential sweep method is used with total chargeduring deposition controlled carefully. The potential is swept fromabout 0.0 V to +1.5 V (vs. Pt quasi-reference). More preferably, thepotential sweep rate is 10-25 mV/s with potential step size between 2and 7 mV, and the total charge during deposition is 7.5 to 12.5 mC/cm².Polymer films deposited using these parameters have a blue-violetcoloration, are extremely homogeneous and uniform, and yield a % T, at575 nm (the approximate wavelength of maximum absorption for thispolymer), of 45% to 50%. They display the most optimal electrochromicperformance in devices, as characterized by light/dark contrast (Delta %T at 575 nm), switching time, cyclability and durability.

In preferred embodiments of the invention, electrochemical deposition ofthe cathodically coloring polymer is provided with a potential sweepmethod rather than a potentiostatic method; the latter yields poor filmswith poor electrochromic performance. During such deposition, thepotential is swept from about 0.0 V to +1.5 V (vs. Pt quasi-reference),a preferred scan rate is 2 mV/s to 50 mV/s and a preferred potentialstep size from 1 mV to 10 mV. A more preferred scan rate is 10-20 mV/s,and a more preferred potential step size is between 2 and 4 mV; apreferred total charge is 11 to 19 mC/cm² and a preferred % T of thefilm as deposited at 575 nm is 41% to 55%. Highly uniform, homogeneouspolymer films with a dark blue/violet coloration are obtained. A typicalsuch electrochemical deposition is described in EXAMPLE 11. Based onestablished principles of electrochemical polymerization of conductingpolymers (see Chandrasekhar, 1999, Chapters 1-3), and without beingconfined to any particular theory of operation, it is highly likely thatthe polymer chain in this copolymer contains random units of the threemonomers in the proportions noted above (e.g. 5:1:1) such that theextended conjugation in the polymer chain has properties correspondingto contributions from the strongly electron-withdrawingchloro-substituent and the less electron-withdrawing bromo-substituent,along with the “neutral” unsubstituted monomer. Additionally, the largersubstituents (benzyl, chloro-benzyl, bromo-benzyl) impose greaterstructural order (reflected, e.g. in less cross -linking) and thusfurther improve the extended conjugation of the resulting conductingpolymer. This unique extended conjugation and unique stereochemistryleads to improved electrochromic properties, as described further below.

EXAMPLES 8 and 10 describe the electrochemical depositions of othercathodically -coloring polymers. COMPARATIVE EXAMPLE 9 describes suchdeposition using a potentiostatic (constant potential) method; thisyields poorly formed, non-uniform polymer susceptible to cracking anddisplaying much poorer electrochromic properties.

Anodically Coloring Polymer

The anodically coloring polymers used in the electrochromic device maybe those materials known in the art and may include but are not limitedto: poly(pyrrole); the structurally related poly(aromatic amine) seriescomprising poly(diphenyl amine), poly(4-amino-biphenyl) (Guay et al.,1989) and poly(aniline); poly(N,N′-diphenyl benzidine) (Suzuki et al.,1989); poly(phenylene); poly(phenylene vinylene); poly(allylenevinylene); poly(amino quinoline).

A preferred composition for the anodically coloring polymer is acopolymer of N,N′-diphenyl benzidine, diphenyl amine and4-amino-biphenyl, in a ratio of about 1:1:1 to 50:1:1 to, withelectrochromic performance seen to be superior to that of the pure (i.e.non-copolymer) polymers of these monomers. More preferably, the abovemolar ratio is from about 1:1:1 to about 20:1:1 and even morepreferably, the above molar ratio is about 10:1:1 to 20:1:1. In otherpreferred embodiments, the above molar ratio is about 3:1:1 to 9:1:1,and even more preferably, the above molar ratio is about 4:1:1 to 7:1:1.In a specifically preferred embodiment, the above molar ratio is about5:1:1.

As for the cathodically-coloring copolymers described above, establishedprinciples of electrochemical polymerization of conducting polymers (seeChandrasekhar, 1999, Chapters 1-3) indicate that it is likely that thepolymer chain in this copolymer contains random units of the threemonomers in the proportions used. The properties of the copolymerresulting therefrom are thus a composite of the contributions to theextended conjugation of the individual monomers. Additionally, thepresence of the three monomers, and most especially the N,N′-diphenylsubstituted monomer, is expected to introduce greater structuralregularity in the resulting copolymer. These unique characteristics ofthe copolymer lead to improved electrochromic properties, as describedfurther below. A typical electrodeposition of an anodically-coloringcopolymer is described in EXAMPLE 12.

Another aspect addressed in the present invention is the improvement ofprocedures for preparation of monomer solutions of anodically coloringpolymers described in the prior art, which were found in extensivestudies to either not work or work very poorly. An example of this isthe preparation of the monomer solution of the N,N′-diphenyl benzidine,as described in the work of Suzuki et al. (1989). It was found in therepetition of their procedures for preparation of solutions of thismonomer in N,N′-dimethyl formamide (DMF) and acetonitrile solvents(solutions to be subsequently used in electrochemical polymerization ofthe corresponding polymer, poly(N,N′-diphenyl benzidine)), that: (1) Inthe case of this monomer solution in DMF solvent, no polymer film wasformed on a variety of substrates using a wide variety of chemical andelectrochemical deposition (polymerization) conditions (see COMPARATIVEEXAMPLE 13). (2) And in the case of the monomer solution in acetonitrilesolvent, the solubility of the monomer was so poor and the monomersolution obtained in acetonitrile so dilute that electrochemicaldeposition (polymerization) of even very thin films of polymer took morethan 4 hours and in some cases even longer. Thus, even though in thecase of DMF solvent, the monomer had very high solubility, no polymerdeposited on ITO substrates using a very wide variety of potential sweepand potential step methods. And again, in the case of acetonitrilesolvent, the solubility of the monomer was so poor that an extremelydilute monomer solution, of concentration <0.1 mM, was obtained inacetonitrile. As a result, the potentiostatic electro-polymerization onITO substrates took an inordinately took an inordinately long time andpotential sweep polymerization also yielded very thin films even overseveral hundred sweeps. These unsuccessful studies are described inCOMPARATIVE EXAMPLE 13.

A modified procedure with DMF and acetonitrile solvents of a particularproportion worked well to dissolve this monomer as well as to yield thecorresponding polymer film of acceptable thickness on ITO substrates ina times less than 40 minutes. These studies are described in COMPARATIVEEXAMPLE 13 In particular, it was found that the optimal volume ratio ofacetonitrile to DMF was in the region of 6:1 (v/v %). Ratios of 7:1 orhigher were found to yield very thin polymer films over very long (>2 h)periods of deposition, whilst ratios of 5:1 or lower were found not toyield any polymer films or extremely poor films that showed very pooradhesion to the ITO substrates and could be simply shaken off inacetonitrile solvent. Thus, the ca. 6:1 ratio of DMF:acetonitrile was anunexpected result in that it yielded viable films of polymer, both forthe monomer N,N′-diphenyl benzidine alone, and its copolymers with otheraromatic amine monomers.

Substrate

Preferred substrates are ITO (indium tin oxide) on a chemically inertplastic such as poly(ethylene terephthalate) (PET), i.e. ITO/Mylar®,although any other conductive, transparent substrate may be used, suchas: ITO/glass; doped tin oxide on glass or plastic; very thin (<60 nm)Au on plastic or glass; “NESA” glass; and a more recently studiedsubstrate, carbon nanotubes on plastic or glass. For the preferredsubstrate, ITO/Mylar, the preferred surface resistivity is <60Ohms/square (dimensionless units).

Deposition of Polymers/Copolymers on the Substrate

The polymer is preferably deposited from a nonaqueous monomer solution.A potential sweep method is preferably used in the case of thecathodically coloring polymers and a potential step method is preferablyused in the case of the anodically coloring polymers addressed here.EXAMPLES 8 and 10 describe the electrochemical depositions of othercathodically -coloring polymers. COMPARATIVE EXAMPLE 9 describes suchdeposition of the cathodically coloring polymers using a potentiostatic(constant potential) method; this yields poorly formed, non -uniformpolymer susceptible to cracking and displaying much poorerelectrochromic properties.

Thus, more preferably, in the case of the cathodically coloring polymersaddressed here, a multiple potential sweep method is used with totalcharge during deposition controlled carefully. The potential is sweptfrom about 0.0 V to +1.5 V (vs. Pt quasi-reference). In a particularembodiment, the potential sweep rate is 10-25 mV/s with potential stepsize between 2 and 7 mV, and the total charge during deposition is 7.5to 12.5 mC/cm². Polymer films deposited using these parameters have ablue-violet coloration, are extremely homogeneous and uniform, and yielda % T, at 575 nm (the approximate wavelength of maximum absorption forthis polymer), of 45% to 50%. They display the most optimalelectrochromic performance in devices, as characterized by light/darkcontrast (Delta % T at 575 nm), switching time, cyclability anddurability.

Similar procedures may be used to deposit a copolymer. During suchdeposition, the potential is swept from about 0.0 V to +1.5 V (vs. Ptquasi-reference), a preferred scan rate is 2 mV/s to 50 mV/s and apreferred potential step size from 1 mV to 10 mV. A more preferred scanrate is 10-20 mV/s, and a more preferred potential step size is between2 and 4 mV; a preferred total charge is 11 to 19 mC/cm² and a preferred% T of the film as deposited at 575 nm is 41% to 55%. Highly uniform,homogeneous polymer films with a dark blue/violet coloration areobtained. A typical such electrochemical deposition is described inEXAMPLE 11. Based on established principles of electrochemicalpolymerization of conducting polymers (see Chandrasekhar, 1999, Chapters1-3), and without being confined to any particular theory of operation,it is likely that the polymer chain in this copolymer contains randomunits of the three monomers in the proportions noted above (e.g. 5:1:1)such that the extended conjugation in the polymer chain has propertiescorresponding to contributions from the strongly electron -withdrawingchloro-substituent and the strongly electron-donating amino-substituent,along with the “neutral” unsubstituted monomer. Additionally, the largersubstituents (benzyl, chloro-benzyl, nitro-benzyl) impose greaterstructural order (reflected, e.g. in less cross-linking) and thusfurther improve the extended conjugation of the resulting conductingpolymer. This unique extended conjugation and unique stereochemistryleads to improved electrochromic properties, as described further below.

Electrochromic Device, Including Assembly Thereof and Electrolytes

Electrochromic devices are assembled according to the schematic ofFIG. 1. Typical assemblies are described in EXAMPLE 14 and COMPARATIVEEXAMPLES 15-17.

For the electrolyte for the devices, a gel electrolyte is preferred. Aprocedure for synthesis of a preferred electrolyte, adapted fromelectrolytes presented in the prior art, is described in EXAMPLE 14. Apreferred electrolyte uses a polymer such as poly(methyl methacrylate)(PMMA) or poly(ethyl methacrylate) (PEMA) as a matrix, appropriate saltssuch as Li trifluoromethane sulfonate (Li triflate) and LiBF₄, andplasticizers and/or further solvating agents such as propylenecarbonate, which is an organic solvent (typically used in Li batteryelectrolytes) with a very high b.p., 240° C. Once set, the gelelectrolyte resembles a hard but flexible, rubbery plastic.

As seen in the schematic in FIG. 1, the components of the electrochromicdevices comprise the two conducting polymer electrodes (withcathodically- and anodically-coloring polymers, respectively), theelectrolyte and gaskets for sealing and for containing the electrolyte.The electrolyte is applied to both polymer electrodes as a very thinlayer using a doctor-blade technique. Overnight setting yields acomplete device, which may then be optionally sealed with additionaledge-sealants.

EXAMPLE 14 describes in detail the assembly of a typical dual-polymerdevice. In this case, the cathodically-coloring polymer is a copolymerof 2,2-(bis-4-chloro-benzyl) -3,4-propylenedioxythiophene,2,2-(bis-4-bromo-benzyl)-3,4-propylenedioxythiophene and2,2-dibenzyl-3,4-propylenedioxythiophene and the anodically-coloringpolymer is a copolymer of N,N′-diphenyl benzidine, diphenyl amine and4-amino-biphenyl. COMPARATIVE EXAMPLE 15 describes the assembly ofdual-polymer electrochromic device comprisingpoly(2,2-(bis-4-chloro-benzyl)-3,4-propylenedioxythiophene)(“poly(Cl-Bz-ProDOT)”) as the cathodically coloring polymer and acopolymer of N,N′-diphenyl benzidine, diphenyl amine and 4-amino-biphenyl as the anodically coloring polymer. COMPARATIVE EXAMPLE 16describes the assembly of dual-polymer electrochromic device comprisingthe prior art polymer, poly(isothianaphthene) (PITN), as thecathodically coloring polymer and a copolymer of N,N′-diphenylbenzidine, diphenyl amine and 4-amino-biphenyl as the anodicallycoloring polymer. COMPARATIVE EXAMPLE 17 describes the assembly ofsingle-polymer electrochromic device comprising poly(N,N′-diphenylbenzidine) as the anodically coloring polymer.

Electrochromic Performance of Dual-Polymer and Single-Polymer, IncludingCopolymer Devices

A known cathodically-coloring polymer, poly(isothianaphthene) (PITN),serves as a useful reference and benchmark in the comparison ofdual-polymer devices. The redox potentials of this polymer, PITN, aresomewhat poorly matched to those of virtually all anodically-coloringpolymers, and particularly poorly matched to those of poly(aromaticamines) such as poly(diphenyl amine), poly(4-amino-biphenyl) andpoly(N,N′-diphenyl benzidine). This is further confirmed in the cyclicvoltammogram shown in FIG. 8, which shows cyclic voltammograms of adevice as assembled in COMPARATIVE EXAMPLE 16, i.e. with PITN as thecathodically-coloring polymer and a copolymer of N,N′-diphenylbenzidine, diphenyl amine and 4-amino-biphenyl as theanodically-coloring polymer, between the voltages corresponding to itsextreme light and dark states. The voltammogram is seen to have poorlydefined oxidation peaks. More telling is the poor electrochromicperformance embodied in FIG. 9, which shows the UV-Vis-NIR spectra ofthis device in its extreme light and dark states; the poor contrast(Delta % T) is clearly seen. Nevertheless, being a dual-polymer device,this device shows a switching time <5 s, and cyclability, >2000 cycles.

Another useful comparison is obtained from the performance of the deviceas assembled in COMPARATIVE EXAMPLE 17, i.e. a single-polymerelectrochromic device comprising poly(N,N′-diphenyl benzidine) as theanodically coloring polymer. Its extreme light/dark state electrochromicperformance, seen in FIG. 10, shows a Delta % T at the wavelength ofmaximum absorption of about 40%, which may be considered fair to good.However, the device shows a rather poor switching time, ca. 15 to 20 s,and starts to degrade significantly after about 1000 light/dark cycles.These performance data substantiate the view that single-polymer devicesshow poorer performance than dual-polymer devices.

A relative comparison of the superior electrochromic performance of theelectrochromic devices and systems of the present invention can be seenin the data in FIGS. 11-13. FIG. 11 shows the UV-Vis-NIR spectra in theextreme light/dark states of the dual-polymer device assembled accordingto COMPARATIVE EXAMPLE 15, i.e. withpoly(2,2-(bis-4-chloro-benzyl)-3,4-propylenedioxythiophene)(“Poly(Cl-Bz-ProDOT)”) as the cathodically coloring polymer and acopolymer of N,N′-diphenyl benzidine, diphenyl amine and4-amino-biphenyl as the anodically coloring polymer, along with thedual-polymer device assembled according to EXAMPLE 14, i.e. with acopolymer of 2,2-(bis-4-chloro-benzyl)-3,4-propylenedioxythiophene,2,2-(bis-4-bromo-benzyl)-3,4-propylenedioxythiophene and2,2-dibenzyl-3,4-propylenedioxythiophen] as the cathodically coloringpolymer and a copolymer of N,N′-diphenyl benzidine, diphenyl amine and4-amino-biphenyl as the anodically coloring polymer. It is noted thatthe thicknesses of the copolymers in both devices were prepared to benearly identical, to enable a better direct comparison. It is seen,firstly, that the single-cathodically-coloring -polymer device shows avery large light/dark contrast, about Delta % T 55% at 575 nm (theapproximate wavelength of maximum absorption). Secondly, it is seen thatthe copolymer-cathodically-coloring -polymer device shows significantlyincreased contrast, Delta % T about 60% at 575 nm, and a more broad-bandresponse in the light state, although the dark state is nearly identicalto that of the single-polymer device. FIG. 12 shows switching time datafor the same devices. Although the switching times appear nearlyidentical for the two devices, the copolymer devices again show a largerlight/dark contrast.

The fact that the cathodically-coloring and anodically-coloringcopolymers of the device of EXAMPLE 14 are extremely well matchedelectrochemically, i.e. in terms of their redox potentials, is clearlyseen from the relevant electrochemical, i.e. cyclic voltammetric data,as shown in FIG. 13. A key indicator of this is that the currentsobserved in the redox of the single-polymer devices are much smallerthan those of the composite, dual-polymer device, clearly seen in thefigure. Since, in the case of the dual-polymer device, oxidation orreduction at one electrode is accompanied by a companion, highlyreversible opposite process, i.e. reduction or oxidation, at the otherelectrode, redox of each polymer is much more facile; there is then aconcomitant, very significant increase in the observed current. Inessence, more of the polymer is electroactive and switching in the caseof the dual polymer device as compared to the single polymer devices.

Furthermore, the fact that the cathodically-coloring copolymer, i.e. thecopolymer of 2,2-bis(4-chloro-benzyl)-3,4-propylenedioxythiophene,2,2-bis(4-bromo -benzyl)-3,4-propylenedioxythiophene and2,2-dibenzyl-3,4-propylenedioxythiophene, constitutes a betterelectrochemical match for the anodically-coloring copolymer (thecopolymer of N,N′-diphenyl benzidine, diphenyl amine and4-amino-biphenyl) than the individual polymer,poly(2,2-bis(4-chloro-benzyl)-3,4-propylenedioxythiophene)(P(Cl-Bz-ProDOT)), alone is seen in the cyclic voltammetric data of FIG.14. Here, it is seen that, for polymer films having nearly identicalcharge during deposition (and thus also expected to have nearlyidentical thickness), the voltammogram for the copolymer device is morewell defined and has significantly higher currents than that for theP(Cl-Bz-ProDOT)-only device. Again, this implies that more of thepolymer in the former case is electroactive and switching.

Another advantage possessed by the dual-copolymer devices of the presentinvention is that the light/dark spectra “window” can be shifted up ordown with ease. That is to say, if, e.g., the dark and light statetransmissions (% T) of a device are 8% and 60% respectively (at 575 nm),then with appropriate adjustment of the total charge during depositionof the polymers, i.e. their thickness, the dark and light state % T canbe shifted, e.g., to 2% and 54%, in a nearly linear fashion. This isseen in the light/dark data in FIG. 15. In this figure, although thedark state shows a % T of about 0% in approximately the 550 nm to 630 nmregion, it is important to note that this is somewhat deceptive in termsof the visibility through such a device. Such a device just appearstinted, and is still easily seen through; there is no impediment tovisibility whatsoever, due to the fact that there is significanttransmission at the other visible wavelengths.

Regarding certain specific embodiments of the present invention, thepresent invention encompasses windows, mirrors, flat panel displays,visors, glasses, and camouflage, comprising the complimentaryelectrochromic devices of the present invention.

The following examples describe the invention in further detail. Theseexamples are provided for illustrative purposes only, and should in noway be considered as limiting the invention.

EXAMPLES Example 1 Typical Synthesis of Monomer,2,2-(bis-4-chlorobenzyl)-3,4-propylenedioxythiophene(“3,3-Bis(4-chlorobenzyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]-dioxepine”)(“Cl-Bz-ProDOT”)

a. Synthesis of initial intermediate, diethyl bis(4-chloro-benzyl)malonate (Scheme, FIG. 4): The synthesis was carried out under inertatmosphere with dry Argon gas utilizing a balloon apparatus. To a 250 mLround bottom flask was added 11.2 g (0.0545 mol) of 4-chlorobenzylbromide, 17.0 g (0.123 mol) of potassium carbonate and 100 mL ofanhydrous DMF. The neck of the flask was closed with a rubber septum andthe flask was purged with Ar. A rubber balloon/needle apparatus wasfilled with Ar and inserted into the septum. After the balloon wasattached, 3.3 mL (0.022 mol) of diethyl malonate was inserted via asyringe and the flask was heated to 100° C. for 16 h. The flask wascooled to room temperature and the reaction mixture was poured into 200mL of water. The product was extracted with diethyl ether. The etherlayer was washed three times with 100 mL of water and once with 100 mLof brine. The ether layer was dried with MgSO₄ and filtered. Solvent wasremoved in vacuo. The residue was recrystallized from hexanes to give2.87 g (32%). Identity of intermediates and products were confirmed viaTLC and NMR (proton, ¹³C).

b. Alternate synthesis of initial intermediate, diethylbis(4-chloro-benzyl) malonate (Scheme, FIG. 4): The synthesis wascarried out under inert atmosphere with dry Argon gas utilizing aballoon apparatus. To a 250 mL round bottom flask was added 8.8 mL(0.0746 mol) of 4-chlorobenzyl chloride, 17.0 g (0.123 mol) of potassiumcarbonate, 0.59 g tetrabutylammonium triflate (0.00150 mol) and 80 mL ofanhydrous toluene. The mixture was heated to reflux for 16 h. Thesolution was cooled to room temperature. The insoluble salts werefiltered and washed thoroughly with dichloromethane. The solvents wereremoved in vacuo. Column chromatography was performed on the residuewith a silica gel column (25 cm×2.5 cm) using a gradient of pure hexanesto 20% (v/v) dichloromethane in hexanes as the eluent. 3.3 g (11%) ofthe desired material was obtained. Identity of intermediates andproducts were confirmed via TLC and NMR (proton, ¹³C)

c. Reduction of diethyl bis-(4-chlorobenzyl) malonate to2,2-bis(4-chloro -benzyl)-1,3-propandiol (Scheme, FIG. 4): To a 250 mLthree neck round bottom flask was added 1.92 g (50.5 mmol) of lithiumaluminum hydride. The flask was purged with Ar and cooled to 0° C. 20 mLof anhydrous THF was added to the flask. To this flask was added 3.3 g(8.06 mmol) of diethyl bis(4-chlorobenzyl) malonate dissolved in 15 mLTHF. The addition was done slowly via a syringe at approximately adropwise addition pace. The mixture was stirred overnight. Afterstirring, the mixture was cooled to 0° C. and 1.92 mL of de -ionizedwater was added very slowly. After this addition 1.92 mL of 15% sodiumhydroxide was added then 5.76 mL of de-ionized water. The mixture wasstirred for 1 h. The solid was filtered off and thoroughly washed withdiethyl ether. The solvent was removed in vacuo. Column chromatographywas performed on the residue with a silica gel column (25 cm×2.5 cm)using a gradient of pure hexanes to 60% (v/v) ethyl acetate in hexanesas the eluent. 2.58 g (98%) of the desired material was obtained. IR,¹HNMR, ¹³C NMR in addition to TLC were used to confirm identity of theproduct.

d. Alternate reduction of diethyl bis-(4-chlorobenzyl) malonate to2,2-bis(4-chloro-benzyl)-1,3-propandiol (Scheme, FIG. 4): To a 50 mLround bottom flask was added 2.87 g (7.01 mmol) of diethylbis(4-chlorobenzyl) malonate. The neck of the flask was closed with arubber septum and the flask was purged with Ar. A rubber balloon/needleapparatus was filled with Ar and inserted into the septum. To the flaskwas added 15 mL (30 mmol) of 2.0 M LiBH₄. The flask was heated to 50° C.overnight. It was then cooled to 0° C. and 12 mL of a saturated solutionof (NH₄)₂SO₄ was slowly added to the flask. The solution was then pouredinto a 250 mL separatory funnel and the product was extracted with ethylacetate. The organic layer was washed twice with 100 mL of water andonce with brine. The solution was dried with MgSO₄. Solvent was removedin vacuo to give 1.65 g (72%) of the alcohol. IR, ¹HNMR, ¹³CNMR inaddition to TLC were used to confirm identity of the product. Thismaterial was used without purification in next step.

e. Reaction of 2,2-bis(4-chloro-benzyl)-1,3-propanediol with3,4-dimethoxythiophene to produce the final monomer,2,2-(bis-4-chlorobenzyl)-3,4-propylenedioxythiophene((“3,3-Bis(4-chlorobenzyl)-3,4-dihydro-2H -thieno[3,4-b][1,4]-dioxepine”“Cl-Bz-ProDOT”) (Scheme FIG. 4): To a 500 mL round bottom flask wasadded 1.65 g (5.07 mmol) 2,2 bis(4-chlorobenzyl)-1,3 propanediol, 0.200g (1.05 mmol) p-toluenesulfonic acid monohydrate and 100 mL of toluene.The neck of the flask was closed with a rubber septum and the flask waspurged with N₂. A rubber balloon/needle apparatus was filled with N₂ andinserted into the septum. To the mixture was added 0.49 mL (4.11 mmol)of 3,4 dimethoxythiophene and the flask was heated to 80° C. for 1 d(˜17 h). The flask was cooled to room temperature and the solvent wasremoved in vacuo. Column chromatography was performed on the residuewith a silica gel column (25 cm×2.5 cm) using a gradient of pure hexanesto 30% (v/v) dichloromethane in hexanes as the eluent. 1.03 g (50%) ofthe desired material was obtained. IR, ¹HNMR, ¹³CNMR in addition to TLCwere used to confirm identity of the product.

Comparative Example 2 Alternative Syntheses of Monomer,2,2-(bis-4-chlorobenzyl)-3,4-propylenedioxythiophene (“Cl-Bz-ProDOT”)

The synthesis of diethyl bis(4-chloro-benzyl) malonate was carried outin a manner substantially identical to that described in EXAMPLE 1, Stepa. above, except that the proportionate molarity of triethyl amine wassubstituted for the K₂CO₃. The reaction was observed to be extremelyslow and no product was obtained over a period of 72 hours.

Comparative Example 3 Alternative Syntheses of Monomer,2,2-(bis-4-chlorobenzyl)-3,4-propylenedioxythiophene (“Cl-Bz-ProDOT”)

The synthesis of diethyl bis(4-chloro-benzyl) malonate was carried outin a manner substantially identical to that described in EXAMPLE 1, Stepa. above, except that the proportionate molarity of di-isopropyl ethylamine was substituted for the K₂CO₃. The reaction was observed to beextremely slow and no product was obtained over a period of 72 hours.

Comparative Example 4 Alternative Syntheses of Monomer,2,2-(bis-4-chlorobenzyl)-3,4-propylenedioxythiophene (“Cl-Bz-ProDOT”)

The synthesis of diethyl bis(4-chloro-benzyl) malonate was carried outin a manner substantially identical to that described in EXAMPLE 1, Stepa. above, except that the proportionate molar quantity of 0.9 M solutionof Na ethoxide in ethanol was substituted for the K₂CO₃. No reaction wasobserved to occur and no product was obtained over a period of 72 hours.

Example 5 Typical Synthesis of Monomer,2,2-(bis-4-bromobenzyl)-3,4-propylenedioxythiophene(“3,3-Bis(4-bromobenzyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]-dioxepine”)(“Br-Bz-ProDOT”)

a. Synthesis of initial intermediate, diethyl bis(4-bromo-benzyl)malonate (Scheme, FIG. 5): To a 250 mL round bottom flask was added 8.63g (0.0345 mol) of 4-bromobenzyl bromide, 17.0 g (0.123 mol) of potassiumcarbonate and 100 mL of anhydrous DMF. The neck of the flask was closedwith a rubber septum and the flask was purged with Ar. A rubberballoon/needle apparatus was filled with Ar and inserted into theseptum. After the balloon was attached, 2.2 mL (0.014 mol) of diethylmalonate was inserted via a syringe and the flask was heated to 100° C.for 16 h. The flask was cooled to room temperature and the reactionmixture was poured into 200 mL of water. The product was extracted withdiethyl ether. The ether layer was washed three times with 100 mL ofhalf brine and once with 100 mL of brine. The ether layer was dried withMgSO₄ and filtered. Solvent was removed in vacuo. The residue wasrecrystallized from hexanes to give 1.42 g (20%). IR, ¹HNMR, ¹³CNMR inaddition to TLC were used to confirm identity of the product.

b. Synthesis of intermediate, 2,2 Bis(4-bromobenzyl)-1,3 propanediol(Scheme, FIG. 5): To a 50 mL round bottom flask was added 1.42 g (2.85mmol) of diethyl bis(4-bromobenzyl) malonate. The neck of the flask wasclosed with a rubber septum and the flask was purged with Ar. A rubberballoon/needle apparatus was filled with Ar and inserted into theseptum. To the flask was added 15 mL (30 mmol) of 2.0 M LiBH₄. The flaskwas heated to 50° C. overnight. It was then cooled to 0° C. and 12 mL ofa saturated solution of (NH₄)₂SO₄ was slowly added to the flask. Anadditional 50 mL of water was added to the mixture and the solution wasthen poured into a 250 mL separatory funnel. The product was extractedwith ethyl acetate and the organic layer was washed twice with 100 mL ofwater and once with brine. The solution was dried with MgSO₄. Solventwas removed in vacuo to give 1.00 g (85%) of the alcohol. This materialwas used without purification in next step. IR, ¹HNMR, ¹³CNMR inaddition to TLC were used to confirm identity of the product.

c. Reaction of 2,2-bis(4-bromo-benzyl)-1,3-propanediol with3,4-dimethoxythiophene to produce the final monomer,2,2-(bis-4-bromobenzyl)-3,4-propylenedioxythiophene((“3,3-Bis(4-bromobenzyl)-3,4-dihydro-2H -thieno[3,4-b][1,4]-dioxepine”“Br-Bz-ProDOT”) (Scheme, FIG. 5): To a 200 mL round bottom flask wasadded 1.00 g (2.41 mmol) 2,2 bis(4-bromobenzyl)-1,3 propanediol, 0.1 g(0.5 mmol) p-toluenesulfonic acid monohydrate and 30 mL of toluene. Theneck of the flask was closed with a rubber septum and the flask waspurged with N₂. A rubber balloon/needle apparatus was filled with N₂ andinserted into the septum. To the mixture was added 0.34 mL (2.85 mmol)of 3,4 dimethoxythiophene and the flask was heated to 80° C. for 1 d (17h). The flask was cooled to room temperature and the solvent was removedin vacuo. Column chromatography was performed on the residue with asilica gel column (25 cm×2.5 cm) using a gradient of pure hexanes to 30%(v/v) dichloromethane in hexanes as the eluent. 0.153 g (13%) of thedesired material was obtained. IR, ¹HNMR, ¹³CNMR in addition to TLC wereused to confirm identity of the product.

It is important to note that the bromo-substituted derivative monomerprovides a very facile route to monomers substituted with alkyl- andother substituents.

Example 6 Typical Synthesis of Monomer,2,2-(bis-4-nitrobenzyl)-3,4-propylenedioxythiophene(“3,3-Bis(4-nitrobenzyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]-dioxepine”)(“Nitro-Bz-ProDOT”)

a. Synthesis of the intermediate2,2-Dimethyl-5,5-di(4-nitrobenzyl)-1,3-dioxane-4,6-dione (See Scheme,FIG. 6): An adaptation of the procedure of Fillion et al. (2005) wasfollowed. To a 1 L round bottom flask was added 11.23 g (0.0520 mol) of4-nitrobenzyl bromide, 3.0 g (0.0208 mol) of2,2-dimethyl-1,3-dioxane-4,6-dione (Meldrum's acid), 9.5 g (0.0687 mol)of potassium carbonate and 150 mL of DMF. This mixture was stirred for12 h then 700 mL of water was added to the round bottom flask. Theresulting precipitate was collected and washed with water. Thisprecipitate give was recrystallized from a methanol/dichloromethanemixture to give 7.39 g (86%). IR, ¹HNMR, ¹³CNMR in addition to TLC wereused to confirm identity of the product.

b. Synthesis of the intermediate 2,2-Bis(4-nitrobenzyl)malonic acid (SeeScheme, FIG. 6): An adaptation of the procedure described byTiefenbacher and Rebek (2012) was followed. To a suspension of 5.33 g(12.9 mmol) of 2,2-dimethyl-5,5-di(4-nitrobenzyl)-1,3-dioxane-4,6-dionein 60 mL of a 9:1 mixture of THF to water was added 1.11 g (46.3 mmol)LiOH. This suspension was stirred for ˜17 h. After stirring, 100 mL ofwater was added to the suspension. The aqueous solution was washed twicewith 50 mL of diethyl ether. The aqueous solution was then acidified topH=1. The product was extracted with ethyl acetate. The ethyl acetatesolution was washed once with 100 ml of water and once with 100 mL ofbrine. The ethyl acetate solution was dried with MgSO₄ and the solventwas removed in vacuo to yield 4.21 g (87%) of the desired material. IR,¹HNMR, ¹³CNMR in addition to TLC were used to confirm identity of theproduct.

c. Synthesis of the intermediate 2-Bis(4-nitrobenzyl)propane-1,3-diol(See Scheme, FIG. 6): An adaptation of the procedure described byTiefenbacher and Rebek (2012) was followed. A 500 mL round bottom flaskwas purged with Ar and the neck of the flask was closed with a rubberseptum. A rubber balloon/needle apparatus was filled with Ar andinserted into the septum. To the 500 mL round bottom flask was added 67mL (67 mmol) of a 1.0 M solution of BH₃ in THF. The septum on the roundbottom flask was replaced with a 125 mL addition funnel and a septum wasinserted into the top of addition funnel. The whole setup was purgedagain with Ar and a rubber balloon/needle apparatus was filled with Arand inserted into the septum. To the addition funnel was added 4.21 g(11.2 mmol) of 2,2-bis(4-nitrobenzyl)malonic acid in 60 mL of THF. Themalonic acid solution was added to BH₃ solution dropwise over a periodof 2 h. After the addition the entire solution was stirred for 17 h.After the stirring, 20 mL of water was added dropwise to the solution.20 mL of a 1 M HCl was added to the solution and this mixture wasstirred for 1.5 h. The product was then extracted with ethyl acetate(three times, 50 mL) and dried with MgSO₄. The solvent was removed invacuo. To the resulting residue was added 50 mL of THF and 20 mL of a 1M HCl solution. This mixture was stirred for 1.5 h. The THF was removedin vacuo and 100 mL of water was added to the residue. The product wasextracted with ethyl acetate (three times, 50 mL) and dried with MgSO₄.Solvent was removed in vacuo to give 2.73 g (70%) of material. IR,¹HNMR, ¹³CNMR in addition to TLC were used to confirm identity of theproduct.

d. Synthesis of the final monomer,2,2-(bis-4-nitrobenzyl)-3,4-propylenedioxythiophene(“3,3-Bis(4-nitrobenzyl)-3,4-dihydro-2H -thieno[3,4-b][1,4]-dioxepine”)(“Nitro-Bz-ProDOT”) (See Scheme, FIG. 6): To a 200 mL round bottom flaskwas added 2.15 g (6.21 mmol) 2,2 bis(4nitrobenzyl)-1,3 propanediol, 0.2g (1 mmol) p-toluenesulfonic acid monohydrate and 150 mL of toluene. Theneck of the flask was closed with a rubber septum and the flask waspurged with N₂. A rubber balloon/needle apparatus was filled with N₂ andinserted into the septum. To the mixture was added 0.90 mL (7.55 mmol)of 3,4 dimethoxythiophene and the flask was heated to 80° C. for 1 d (17h). The flask was cooled to room temperature and the solvent was removedin vacuo. Column chromatography was performed on the residue with asilica gel column (15 cm×2.5 cm) using a gradient of pure hexanes to 60%(v/v) dichloromethane in hexanes as the eluent. A second column (25cm×2.5 cm) was carried out using a gradient of pure hexanes to 35% (v/v)ethyl acetate in hexanes as the eluent. 0.388 g (15%) of the desiredmaterial was obtained. IR, ¹HNMR, ¹³CNMR in addition to TLC were used toconfirm identity of the product.

Example 7 Typical Synthesis of Monomer,2,2-(bis-4-aminobenzyl)-3,4-propylenedioxythiophene(“3,3-Bis(4-aminobenzyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]-dioxepine”)(“Amino-Bz-ProDOT”)

(See Scheme, FIG. 7).

To a 200 mL round bottom flask was added 0.307 g (0.722 mmol) of3,3-Bis(4-nitrobenzyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]-dioxepine, 2.1g (9.3 mmol) of tin(II) chloride dihydrate and 50 mL of ethyl acetate.The solution was heated to reflux for overnight. After heating, themixture was allowed to cool to room temperature. After cooling, 20 mL ofa 0.25 M solution of sodium carbonate and 100 mL of dichloromethane wereadded. This mixture was vigorously stirred for 30 minutes. The mixturewas then filtered through a celite pad and poured into a 500 mLseparatory funnel. The organic layer was removed and washed twice with50 mL of water and once with 50 mL of brine. The solution was dried withMgSO₄ and the solvent was removed in vacuo to give the product,3,3-bis(4-aminobenzyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]-dioxepine, inquantitative yield. IR, ¹HNMR, ¹³CNMR in addition to TLC were used toconfirm identity of the product.

Example 8 Electrochemical Deposition of the (Cathodically-Coloring)Polymer, Poly(2,2-(bis-4-chloro-benzyl)-3,4-propylenedioxythiophene)(“Poly(Cl-Bz-ProDOT)”) from Monomer Solution

The monomer produced as in EXAMPLE 1 was placed in a vacuum oven forabout 0.5 hour before preparation of the deposition solution. Litrifluoromethane sulfonate (Li triflate) was dried in an oven at 50-55°C. overnight before use. Acetonitrile was dried using activatedmolecular sieves. A stock solution of 250 mL of 0.4 M Li triflate SulfI/acetonitrile was prepared. A 4 mM solution of the Cl-BzProDOT monomerdeposition solution was prepared by adding the appropriate quantity ofthe monomer to the 250 mL stock solution in a conical flask withstifling. A yellow deposition solution was obtained. The polymer,poly(Cl-Bz-ProDOT) was deposited on ITO/Mylar (preferred surfaceresistivity <60 Ohms/square, dimensionless units) using a 3 electrodeconfiguration, with graphite counter electrode and Pt wirequasi-reference electrode. A multiple potential sweep method was used todeposit polymer, with the number of sweeps dependent on the thickness ofpolymer desired, which was monitored by measuring the total chargedeposited using standard electrochemical methods. The optimal totalcharge during deposition was found to be 7.5 to 12.5 mC/cm², for filmsshowing the best performance in devices; such films had a typical % T,at 575 nm, of 45% to 50%. A potential sweep method was found to besuperior to a potentiostatic method (see COMPARATIVE EXAMPLE 9). In atypical method, potential was swept from 0 to +1.5 V (vs. Pt Q-R), at ascan rate of 10-25 mV/s, with potential step size between 2 and 7 mV. Amost preferred scan rate was 12.5 to 22 mV/s and a most preferred stepsize 4 mV. A small difference in the scan rate, e.g. a rate of 17 mV/svs. 13 mV/s, made a significant difference in the darkness of the filmsobtained and thus their suitability for the fabrication of “very dark”or “very light” devices. After deposition, the polymer film was held atan applied potential of 0.0V for 1 min, then immersed from thedeposition solution while at this potential. Films were rinsed withacetonitrile, soaked in 0.2 M Li triflate/acetonitrile solution for 1min, rinsed with acetonitrile, and dried at 50 to 75° C. Highly uniform,homogeneous polymer films with a blue/violet coloration were obtained.

Comparative Example 9 Alternative Electrochemical Deposition of the(Cathodically-Coloring) Polymer,Poly(2,2-(bis-4-chloro-benzyl)-3,4-propylenedioxythiophene)(“Poly(CI-Bz-ProDOT)”) from Monomer Solution

A film of poly(Cl-Bz-ProDOT) was deposited on ITO/Mylar using aprocedure identical to that of EXAMPLE 8, except that in place of thepotential sweep method described, a potentiostatic (constant potential)method was used. The applied potential was held at +0.9 V in oneexperiment, and +1.1 V in a second, these voltages being carefullyselected from the linear sweep voltammogram of the deposition solution.Total charge was carefully monitored and held close to the optimumvalues listed in EXAMPLE 8. The switching time of electrochromic devicesmade with these films was significantly slower (about 10 s vs. about 1s) and their light/dark contrast significantly poorer (Delta % T atwavelength of maximum absorbance 30% to 50% lower), than those ofEXAMPLE 8, i.e. using the potential sweep method. Additionally, somefilms exhibited minor cracks on drying.

Example 10 Electrochemical Deposition of the (Cathodically-Coloring)Polymer, Poly(2,2-(bis-4-bromo-benzyl)-3,4-propylenedioxythiophene)(“Poly(Br-Bz-ProDOT)”, from Monomer Solution

The monomer produced as in EXAMPLE 5 was used to prepare a depositionsolution and then to electrochemically deposit films of the polymer,Poly(2,2-(bis-4-bromo -benzyl)-3,4-propylenedioxythiophene)(“Poly(Br-Bz-ProDOT)”, on ITO/Mylar substrates. This was done in amanner substantially identical to that described in EXAMPLE 8 above,except with the following changes: (1) Monomer solution concentrationused was identical (4 mM). (2) The optimal total charge duringdeposition was found to be 10.5 to 15.0 mC/cm², for films showing thebest performance in devices; such films had a typical % T, at 575 nm, of40% to 47%. (3) In the potential sweep method used, potential was sweptfrom −0.3 to +1.7 V (vs. Pt Q-R), at a scan rate of 10-20 mV/s, withpotential step size between 2 and 4 mV. A most preferred scan rate was12.5 to 15 mV/s and a most preferred step size 2 mV. Highly uniform,homogeneous polymer films with a greenish-blue coloration were obtained.

Example 11 Electrochemical Deposition of the (Cathodically-Coloring)Copolymer of 2,2-(bis-4-chloro-benzyl)-3,4-propylenedioxythiophene,2,2-(bis-4-bromo-benzyl)-3,4-propylenedioxythiophene, and2,2-dibenzyl-3,4-propylenedioxythiophene from Monomer Solution

The monomers, 2,2-(bis-4-chloro-benzyl)-3,4-propylenedioxythiophene,2,2-(bis-4-bromo-benzyl)-3,4-propylenedioxythiophene, and2,2-dibenzyl-3,4-propylenedioxythiophene, were used to prepare adeposition solution and then to electrochemically deposit films of thecorresponding copolymer on ITO/Mylar substrates. This was done in amanner substantially identical to that described in EXAMPLE 8 above,except with the following changes: (1) The individual monomerconcentrations in the deposition solution were: 2,2-(bis-4-chloro-benzyl)-3,4-propylenedioxythiophene, 0.5 mM;2,2-(bis-4-bromo-benzyl)-3,4-propylenedioxythiophene, 0.5 mM;2,2-dibenzyl-3,4-propylenedioxythiophene, 5 mM. (2) The optimal totalcharge during deposition was found to be 11 to 19 mC/cm², for filmsshowing the best performance in devices; such films had a typical % T,at 575 nm, of 41% to 55%. (3) In the potential sweep method used,potential was swept from 0.0 to +1.7 V (vs. Pt Q-R), at a scan rate of10-20 mV/s, with potential step size between 2 and 4 mV. A mostpreferred scan rate was 11 to 14 mV/s and a most preferred step size 4mV. Highly uniform, homogeneous polymer films with a dark blue/violetcoloration were obtained.

Example 12 Electrochemical Deposition of the (Anodically-Coloring)Copolymer of N,N′-Diphenyl Benzidine, Diphenyl Amine and4-Amino-Biphenyl from Monomer Solution

Preparation of the Electrodeposition (i.e., ElectrochemicalPolymerization) Solution: 7.5 g of the monomer N,N′-diphenyl benzidinewere added to 700 mL of dry acetonitrile. The mixture was refluxed overca. 4 h in a N₂ atmosphere in an appropriately sized 3-neck round bottomflask (reflux temperature approximately 83° C.). At the end of thisperiod of reflux, 120 mL of dry N,N′-dimethyl formamide (i.e. 5.83:1 v/v% ratio, acetonitrile:DMF) were added slowly to this mixture. Thetemperature at first dropped slightly and then increased to ca. 87° C.Reflux was continued for ca. 2 h, the temperature remaining ca. 87° C.The entire solution was then sealed under N₂ and allowed to coolovernight. To this solution is added with stifling previously dried Litriflate salt in a proportion of ca. 6.24 g per 100 mL of solution. Thissolution may be used as is for electrochemical polymerization, if it isdesired to produce the single polymer, poly(N,N′-diphenyl benzidine). Ifhowever it is desired to produce copolymers then to this solution areadded, with stifling, quantities of the monomers diphenyl amine and4-amino-biphenyl so as to obtain final concentrations of each monomer ofin the ratios N,N′-diphenyl benzidine:diphenyl amine:4-amino-biphenyl ofca. 5:1:1. Previously dried Li triflate salt was added to the solutionwith stifling in a proportion of ca. 6.2 g per 100 mL of solution. Theend result in either case is “stock solution” which is then used for allelectrodepositions (i.e. electrochemical polymerizations).

Electrodeposition (Electrochemical Polymerization from MonomerSolution): The above stock solution was used for electropolymerizationof the subject polymer onto ITO/Mylar substrates using a potentiostatic(i.e., constant potential) mode of deposition. A 3-electrode setup, withgraphite counter and Pt wire quasi-reference electrodes was used. Apotentiostatic (i.e., constant potential) deposition, at +0.5 V (vs. Ptquasi-reference) was used. Charge during deposition was monitoredcoulometrically, and set to between 140 and 200 mC/cm², for very lightand very dark films respectively. For most preferred films yieldingelectrochromic devices with the best performance, a charge of 160 mC/cm²yielding a corresponding transmission at 575 nm of 69% T were mostpreferred. Films were immersed at an applied voltage of 0.0 V, rinsedwith acetonitrile, soaked in 0.4 M Li triflate/acetonitrile solution for1 min, re -rinsed, and dried at ca. 60° C. for 1 hr. Highly homogeneous,uniform, green-blue films were obtained.

Comparative Example 13 Electrochemical Deposition of the(Anodically-Coloring) Polymer of N,N′-Diphenyl Benzidine, from MonomerSolution in Different Solvents

Solutions of the monomer, N,N′-diphenyl benzidine (Dabs), of severalconcentrations ranging from 1 mM to 100 mM were prepared inN,N′-dimethyl formamide (DMF), according to the methodology described bySuzuki et al. (1989). Dry Li triflate was added to this solution toyield a concentration of 0.4 M. Electrochemical deposition(electro-polymerization) of the corresponding polymer was attempted onITO/Mylar substrates using a variety of potential step and potentialsweep methods. These included the methods described by Suzuki et al.(1989), potential step methods at applied potentials (all vs. Ptquasi-reference) between +0.2 V and +1.5 V, and potential sweep methodsbetween 0.0 V and +1.7 V (all vs. Pt quasi -reference) (cf. EXAMPLES 8,10, 11, 12 and COMPARATIVE EXAMPLE 9). While a copious colored exudatewas observed at the ITO/Mylar substrate during electro-deposition,likely indicating oligomer formation, no polymer film formation wasobserved on the substrate, even at times as long as 4 h. Other salts,e.g. with the above triflate anion substituted by tosylate,tetrafluoroborate and other anions, in concentrations from 0.1 M to 1 M,were also tested in the deposition solution with identical, unsuccessfulresults.

Electro-depositions of this monomer were also tested from acetonitrilesolution, again attempting to reproduce the methodology of Suzuki et al.(1989). For this, the saturated solution of the monomer in acetonitrile,prepared as described in EXAMPLE 12, was used, with 0.4 M Li triflateadded thereto. Potentiostatic deposition at potential ranging from +0.5to +1.5 V (vs. Pt quasi-reference), and potential sweep methods asdescribed in EXAMPLE 11, were tested. Using the potential step methods,times in excess of 2 h were required to obtain even a very thin film ofthe polymer (poly(N,N′-diphenyl benzidine) on the ITO substrates. Usingpotential sweep methods, more than 200 sweeps were required to obtainsimilar, very thin polymer films. Again, besides Li triflate, othersalts were also tested in the deposition solution in concentrations from0.1 M to 1 M. These results may be contrasted with those described bySuzuki et al. (1989), wherein a few potential sweeps are purportedlysaid to yield a thick polymer film on ITO substrates.

As described in EXAMPLE 12 above, to successfully dissolve the monomerN,N′-diphenyl benzidine in an appropriate solvent (to subsequentlyelectro-polymerize it therefrom), it was found that an optimal solventwas DMF:acetonitrile in ca. 6:1 v/v % proportion. Several other ratiosof DMF:acetonitrile were tested. It was found that, using the severaldifferent conditions of potential step, potential sweep and added salt(electrolyte) as described above, ratios of DMF:acetonitrile of 7:1 orhigher were found to yield very thin polymer films over very long (>2 h)periods of deposition, whilst ratios of 5:1 or lower were found not toyield any polymer films or extremely poor films that showed very pooradhesion to the ITO substrates and could be simply shaken off inacetonitrile solvent. Thus, the ca. 6:1 ratio of DMF:acetonitrileprovided an unexpectedly advantageous result in that it yielded viablefilms of polymer, both for the monomer N,N′-diphenyl benzidine alone,and its copolymers with other aromatic amine monomers, as described inEXAMPLE 12.

Example 14 Assembly of Dual-Polymer Electrochromic Device Comprising[Copolymer of 2,2-(bis-4-chloro-benzyl)-3,4-propylenedioxythiophene,2,2-(bis-4-bromo-benzyl)-3,4-propylenedioxythiophene and2,2-dibenzyl-3,4-propylenedioxythiophene] as the Cathodically ColoringPolymer and [Copolymer of N,N′-Diphenyl Benzidine, Diphenyl Amine and4-Amino-Biphenyl] as the Anodically Coloring Polymer

a. Components: An electrochemical device was fabricated substantiallyfollowing the schematic depicted in FIG. 1. For “CP1”, i.e. ConductingPolymer #1, the cathodically-coloring polymer, the polymer film preparedas in EXAMPLE 11 above was used. For “CP2”, i.e. Conducting Polymer #2,the anodically-coloring polymer, the polymer film prepared as in EXAMPLE12 above was used.

b. Electrolyte: A 125 mL wide-mouth conical flask was used. 3 g of Litriflate, previously dried (overnight, 60° C., vacuum oven) were addedto 70 g of dry acetonitrile (ACS reagent grade, dried over molecularsieves) therein with stirring until dissolved. 7 g of poly(methylmethacrylate (PMMA) were added very slowly (to prevent clumping) to thestirring mixture with mild heat, over 0.5 hr. Now 20 g of dry propylenecarbonate (ACS reagent grade, dried over molecular sieves) were added tothe mixture, now a solution, which was then allowed to sit withoutstifling for 1 hr. Next, a pipette for N₂ bubbling was introduced intothe flask and slow bubbling with dry N₂ commenced. Slow stirring wasthen commenced and mild heat was applied to the flask to bring thetemperature of the solution to 40° C., taking care to never exceed 50°C. This N₂ bubbling under stirring at ca. 40° C. was continued over aperiod of several hours until the volume reduced to 25 mL, yielding thefinal gel electrolyte as to be used in the electrochromic devices. Inaddition to the above described electrolyte, a large number ofnon-aqueous-based, prior art electrolytes, e.g. those described by Welshet al. (1999), Sapp et al. (1998) Gazotti et al. (1998) and Groenendalet al. (2000) may be used, after suitable (and in some cases,significant) modification to accommodate the particular conductingpolymer combinations used in the present invention.

c. Assembly: Devices were assembled per the schematic of FIG. 1, usingthe above components. The gasket used was typically of polyethylene ofthickness 0.5 to 2.0 mil (ca. 13 to 50 microns). Gel electrolyte wasre-warmed to ca. 30° C. for the procedure. Gaskets were set into placeusing the gel electrolyte as a setting glue. Electrolyte was firstapplied individually to the bulk of both polymer/ITO/Mylar films using adoctor blade method. Devices were then fully assembled, according to theschematic of FIG. 1. They were then clamped together using spring-loaded clamps. The clamped devices were allowed to sit overnight.Excess gel electrolyte from outer surfaces and edges was then cleanedwith a Kimwipe wetted with acetonitrile. Optionally, the edges of thedevice could be sealed with inert, 2-component, polyurethane adhesives.For testing, electrical contact was simply made with alligator clips tothe two electrodes of the devices. For a more permanent attaching ofelectrical lead wires, a special, commercial, space -qualified(low-outgassing) Ag epoxy was used.

Comparative Example 15 Assembly of Dual-Polymer Electrochromic DeviceComprising Poly(2,2-(bis-4-chloro -benzyl)-3,4-propylenedioxythiophene)(“Poly(CI-Bz-ProDOT)”) as the Cathodically Coloring Polymer and[Copolymer of N,N′-Diphenyl Benzidine, Diphenyl Amine and4-Amino-Biphenyl] as the Anodically Coloring Polymer

An electrochemical device was fabricated substantially as described inEXAMPLE 14 except that, in place of the cathodically coloring polymer inthat EXAMPLE, which was a copolymer constituted from three separatemonomers, the simple polymer,poly(2,2-(bis-4-chloro-benzyl)-3,4-propylenedioxythiophene)(“poly(Cl-Bz-ProDOT)”) was used. In particular, it was ensured thepolymer thicknesses, as measured by the total amount of chargedeposited, was nearly identical to those for the corresponding polymersin EXAMPLE 14.

Comparative Example 16 Assembly of Dual-Polymer Electrochromic DeviceComprising [Poly(isothianaphthene) (PITN)] as the Cathodically ColoringPolymer and [Copolymer of N,N′-Diphenyl Benzidine, Diphenyl Amine and4-Amino-Biphenyl] as the Anodically Coloring Polymer

An electrochemical device was fabricated substantially as described inEXAMPLE 14 except that, in place of the cathodically coloring polymer inthat EXAMPLE, poly(isothianaphthene) (PITN) was used. A PITN film waselectrochemically polymerized on ITO/Mylar as described by Chandrasekharet al. (1989). In particular, it was ensured the thickness of theanodically coloring copolymer, as measured by the total amount of chargedeposited, was nearly identical to that for the anodically coloringcopolymer of EXAMPLE 14.

Comparative Example 17 Assembly of Single-Polymer Electrochromic DeviceComprising Poly(N,N′-Diphenyl Benzidine) as the Anodically ColoringPolymer

An electrochemical device was fabricated substantially as described inEXAMPLE 14 except that, in place of the cathodically coloring polymer inthat EXAMPLE, no cathodically coloring polymer, i.e. a blank ITO/Mylarelectrode, was used.

Example 18 Characterization of Electrochromic Devices

Devices as assembled in EXAMPLE 14 and COMPARATIVE EXAMPLES 15-17 werecharacterized via cyclic voltammetry (in 2-electrode mode) andspectroscopically. The latter was carried out using a PC-controlledPerkin-Elmer Lambda 12 double-beam spectrometer, with nothing (i.e.,air) in the reference compartment; this may be contrasted with most ofthe published literature and patent data, which use a “blank” substrateor device, i.e. one of identical construction to the polymer deviceexcept that it does not have any active electrochromic material, asreference. UV-Vis-NIR spectra were taken while the device was heldpotentiostatically at appropriate potentials corresponding to itsextreme light and dark states. For monitoring the switching time, thespectrometer was brought to the wavelength of maximum absorption of thedevices (575 nm for the device of EXAMPLE 14) and the device thenrapidly switched between its extreme light and dark state withappropriate applied voltage. Relevant results are presented in theFIGURES.

Comparative Example 19 Long Term/Lifetime Testing of ElectrochromicDevices Fabricated Gel Electrolyte Testing (as per procedure of EXAMPLE18) of electrochromic devices fabricated as described in Example 14

Three devices were fabricated (per EXAMPLE 14) and tested forelectrochromic performance per the procedures described in EXAMPLE 18above. They were left on the shelf and re-tested after a period of 23months. Their electrochromic performance, measured in terms of the lightand dark state UV-Vis-NIR spectra and switching time, was found to havechanged less than 2.5%. In particular, the light/dark contrast, measuredin units of Delta % T at any particular wavelength, was found to havedegraded less than 2% for two of the devices and to actually haveincreased by 1.5% for the third device. Light/dark switching times,measured at 575 nm, were found to have increased less than 2.5%. Peaksof the cyclic voltammograms of the devices before and after this 23month period were very similar, with mA-scale peaks in all cases.

The invention described and claimed herein is not to be limited in scopeby the specific embodiments herein disclosed, since these embodimentsare intended as illustrations of several aspects of the invention. Anyequivalent embodiments are intended to be within the scope of thisinvention. Indeed, various modifications of the invention in addition tothose shown and described herein will become apparent to those skilledin the art from the foregoing description. Such modifications are alsointended to fall within the scope of the appended claims.

A number of patent and non-patent publications are cited in thespecification in order to describe the state of the art to which thisinvention pertains. The entire disclosure of each of these publicationsis incorporated by reference herein.

Furthermore, the transitional terms “comprising”, “consistingessentially of” and “consisting of”, when used in the appended claims,in original and amended form, define the claim scope with respect towhat unrecited additional claim elements or steps, if any, are excludedfrom the scope of the claim(s). The term “comprising” is intended to beinclusive or open-ended and does not exclude any additional, unrecitedelement, method, step or material. The term “consisting of” excludes anyelement, step or material other than those specified in the claim and,in the latter instance, impurities ordinary associated with thespecified material(s). The term “consisting essentially of” limits thescope of a claim to the specified elements, steps or material(s) andthose that do not materially affect the basic and novelcharacteristic(s) of the claimed invention. All electrochromic devices,compositions and methods for preparing the same that embody the presentinvention can, in alternate embodiments, be more specifically defined byany of the transitional terms “comprising”, “consisting essentially of”and “consisting of”.

REFERENCES

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I claim:
 1. A method for preparing an electrode, wherein the electrodecomprises a polymer comprising N,N′-diphenyl benzidine monomer, themethod comprising the steps of: (a) providing a deposition solutioncomprising the N,N′-diphenyl benzidine monomer; (b) uniformly depositingthe polymer onto a substrate in contact with the deposition solution toyield the electrode; and wherein the deposition solution comprisesdimethylformamide and acetonitrile in a ratio of at least about 6:1 byvolume, respectively.
 2. The method of claim 1, wherein the depositionsolution further comprises one or more of diphenyl amine monomer and4-aminobiphenyl monomer.
 3. The method of claim 1, wherein thedeposition solution comprises N,N′-diphenyl benzidine monomer, diphenylamine monomer, and 4-aminobiphenyl monomer in a molar ratio in the rangeof about 1:1:1: to 50:1:1, respectively.
 4. The method of claim 1,wherein the deposition solution comprises N,N′-diphenyl benzidinemonomer, diphenyl amine monomer, and 4-aminobiphenyl monomer in a molarratio in the range of about 1:1:1: to 20:1:1, respectively.
 5. Themethod of claim 1, wherein the deposition solution comprisesN,N′-diphenyl benzidine monomer, diphenyl amine monomer, and4-aminobiphenyl monomer in a molar ratio in the range of about 1:1:1: to9:1:1, respectively.
 6. The method of claim 1, wherein the depositionsolution comprises N,N′-diphenyl benzidine monomer, diphenyl aminemonomer, and 4-aminobiphenyl monomer in a molar ratio in the range ofabout 3:1:1: to 7:1:1, respectively.
 7. The method of claim 1, whereinthe deposition solution comprises N,N′-diphenyl benzidine monomer,diphenyl amine monomer, and 4-aminobiphenyl monomer in a molar ratio ofabout 5:1:1, respectively.
 8. The method of claim 1, wherein thedeposition solution comprises a salt.
 9. The method of claim 8, whereinthe salt comprises one or more of lithium triflate and LiBF₄.
 10. Themethod of claim 1, wherein the substrate comprises a conductivetransparent substrate.
 11. The method of claim 10, wherein theconductive transparent substrate comprises one or more of anindium-tin-oxide(ITO)/glass substrate, ITO/poly(ethylene terephthalate)(PET) substrate, tin-oxide/glass substrate, tin-oxide/PET substrate,gold/glass substrate, carbon-nanotubes/glass substrate,carbon-nanotubes/PET substrate, and gold/PET substrate.